Green, Grey Or Green-Grey? Decoding Infrastructure Integration and Implementation for Residential Street Retrofits

Lincoln University Digital Thesis

The digital copy of this thesis is protected by the Copyright Act 1994 (New Zealand).

This thesis may be consulted by you, provided you comply with the provisions of the Act and the following conditions of use:

 you will use the copy only for the purposes of research or private study  you will recognise the author's right to be identified as the author of the thesis and due acknowledgement will be made to the author where appropriate  you will obtain the author's permission before publishing any material from the thesis.

Green, Grey or Green-Grey? Decoding infrastructure integration and implementation for residential street retrofits.

A thesis submitted in partial fulfilment of the requirements for the Degree of Master of Landscape Architecture

at L I N C O L N U N I V E R S I T Y New Zealand

by K S E N I A I. A L E K S A N D R O V A

Lincoln University 2016

A B S T R A C T

New-world countries are often characterized by large areas of sprawling post-war suburban development. The streets of these suburbs are often criticized for being unattractive transport corridors that prioritize cars at the cost of the pedestrian environment and ecological health of their neighbourhoods. Green infrastructure (LID) street retrofits, as well as grey infrastructure-dominated traffic calming schemes have been used as partial solutions to the adverse effects of post-war street design. There is, however, a lack of implementation of these measures, along with some confusion as to what is defined as green and grey infrastructure at the street scale. The level to which these schemes are integrated with one another is also unclear.

This paper is based on an international English-language systematic review of academic peer- reviewed literature of built infrastructure elements within residential street settings. The review reports on a body of evidence-based literature, discussing the definitions of green and grey infrastructure at the street scale; along with the barriers and enablers to the implementation of green and grey infrastructure, and the level to which the two are integrated. Barriers and enablers to the successful design and implementation of green and grey infrastructure in residential streets are also investigated.

The physical components of the various infrastructure elements were used to categorize them in order to clearly define the terms green and grey infrastructure within streets. Evidence suggests that there are two ways in which integration of green and grey infrastructure occurs, however only a third of the papers report on green and grey infrastructure integration. Results also show that cost, spatial constraints and resident perception are the most common barriers to the implementation of green and grey infrastructure retrofits in residential streets. Ways to utilize the known barriers and enablers, along with design considerations, are discussed.

The findings presented in this thesis are aimed to provide academics and practitioners with an important series of considerations to help influence the design of street retrofits that achieve a multiple number of social and ecological benefits within a residential setting; in order to help address the adverse social and ecological effects of urbanization and unsustainable post-war development patterns.

K E Y W O R D S

Green infrastructure, Retrofits, Suburban, Streets, Integration, Barriers, Enablers, Implementation, Street design, Infrastructure elements, Street infrastructure, Landscape services

C O N T E N T S

A B S T R A C T ...... II

C O N T E N T S ...... III

T A B L E S A N D F I G U R E S ...... V

I N T R O D U C T I O N ...... 1

1.1 P R O B L E M S T A T E M E N T ...... 1

1.2 R E S E A R C H Q U E S T I O N S A N D O B J E C T I V E S ...... 2 1.2.1 Research Questions ...... 2 1.2.2 Research Objectives ...... 2

1.3 O R G A N I S A T I O N O F T H E S I S ...... 2

L I T E R A T U R E R E V I E W ...... 3

2.1 B A C K G R O U N D ...... 3 2.1.1 Why is the improvement of streets important? ...... 3 2.1.2 Landscape Services – a shift in the perception of street infrastructure ...... 3 2.1.3 Historic background of infrastructure ...... 4 2.1.4 Defining green and grey infrastructure in streets ...... 4

2.2 R E S I D E N T I A L S T R E E T S T H R O U G H H I S T O R Y ...... 6 2.2.1 Roman streets ...... 6 2.2.2 First suburban streets ...... 7 2.2.3 First suburban streets retrofitted for contemporary use ...... 8 2.2.4 Residential streets of the private car era ...... 9

2.3 R E T R O F I T T I N G ...... 12 2.3.1 The case for retrofitting post-war suburbs ...... 12 2.3.2 Retrofitting the suburban streets ...... 12

2.4 D E S I G N A N D I M P L E M E N T A T I O N ...... 16 2.4.1 Known barriers to implementing more landscape services in streets ...... 16 2.4.2 Enablers to implementation of multiple landscape services ...... 16

M E T H O D S ...... 18

3.1 R E S E A R C H D E S I G N ...... 18

3.2 N A R R A T I V E L I T E R A T U R E R E V I E W ...... 18

3.3 S Y S T E M A T I C L I T E R A T U R E R E V I E W ...... 19 3.3.1 Inclusion criteria ...... 20 3.3.2 Searching strategy ...... 21 3.3.3 Method for processing papers ...... 22 iii

3.5 L I M I T A T I O N S O F M E T H O D O L O G Y ...... 25

R E S U L T S ...... 26

4.1 D E F I N I T I O N S A N D F U N C T I O N S ...... 26 4.1.1 Components ...... 26 4.1.2 Functions ...... 26

4.2 I N V E S T I G A T I N G T H E A C A D E M I C L I T E R A T U R E ...... 28 4.2.1 Geographic distribution ...... 28 4.2.2 Methods, Research questions and professional affiliation ...... 29

4.3 I N T E G R A T I O N ...... 31 4.3.1 Street-scale integration ...... 31 4.3.2 Element-scale integration ...... 32 4.3.3 Integration patterns ...... 33

4.4 B A R R I E R S A N D E N A B L E R S ...... 34 4.4.1 Barriers and Enablers for Green Infrastructure ...... 34 4.4.2 Barriers and Enablers for Green-Grey Infrastructure ...... 35 4.4.3 Barriers and Enablers for Grey Infrastructure ...... 36

D I S C U S S I O N ...... 37

5.1 D E F I N I T I O N S A N D F U N C T I O N S ...... 37 5.1.1 Definitions ...... 37 5.1.2 Functions ...... 37

5.2 W H A T I S K N O W N A B O U T T H E B O D Y O F L I T E R A T U R E ? ...... 38 5.2.1 Geographic distribution and infrastructure types ...... 38 5.2.2 Research questions and professional affiliations ...... 38 5.2.3 Relevance to Practice ...... 39 5.2.4 Use of case studies when designing street retrofits ...... 39

5.3 I N T E G R A T I O N ...... 39

5.4 B A R R I E R S A N D E N A B L E R S ...... 41 5.4.1 How could the barriers to implementation be overcome? ...... 41 5.4.2 Considerations for the design of suburban street retrofits ...... 42

C O N C L U S I O N ...... 43

R E F E R E N C E S ...... 45

A P P E N D I X A ...... 53

A P P E N D I X B ...... 54

A P P E N D I X C ...... 55

T A B L E S A N D F I G U R E S

I N T R O D U C T I O N

1.1 P R O B L E M S T A T E M E N T

Well-designed residential streets are integral to the health and well-being of their surrounding communities (Dover & Messengale, 2013).

Suburban streets in New World countries built after the second world war have often been designed to prioritize vehicle movement and parking (Guo, Rivasplata, Lee, Keyon, & Schloeter, 2012). This has lead to significant negative social, ecological and economic impacts, including declining population health due to inactivity (de Nazelle et al., 2011; Garceau et al., 2013), reduced on-road air quality (Colvile et al., 2004) and a cycle of debt and car dependence (Dobson & Sipe, 2008; Horner, 2008). Within the historically wide carriageways of New-World suburban thoroughfares (Southworth & Ben- Joseph, 2003) lies an opportunity to improve the streets through retrofitting them (Després, Brais, & Avellan, 2004; Girling & Helphand, 1997; Novotny, 2013), and integrating green and grey infrastructure elements which have the ability to provide a multitude of services that benefit surrounding residential communities.

Some of the functions provided by green infrastructure elements within streets include fostering and improving citizen health (Annear, Cushman, & Gidlow, 2009), increased aesthetic and economic value within neighbourhoods (Brander & Koetse, 2011; Kong, Yin, & Nakagoshi, 2007) and improved air quality (Hofman, Stokkaer, Snauwaert, & Samson, 2013; Nowak & Crane, 2002). Multiple functions provided by grey infrastructure elements within streets include accommodation of various forms of transit (Selberg, 1996), accommodation of social interaction (May, Tranter, & Warn, 2008) and provision of basic services such as water conveyance, electricity and communication (Costello, Chapman, Rogers, & Metje, 2007).

However, historically, the design of these systems has been advanced by different disciplines and municipal departments (Després et al., 2004; Karndacharuk, Wilson, & Dunn, 2014), and they are often seen as competing land uses (Tjallingii, 2003). Little is known about the extent to which multiple functions are being incorporated into street retrofits, or the barriers and enablers to designing and implementing integrated green and grey infrastructure into residential streets.

1.2 R E S E A R C H Q U E S T I O N S A N D O B J E C T I V E S

1.2.1 Research Questions 1) What are the definitions and functions of infrastructure elements identified as green and grey infrastructure within residential streets?

2) What is known about the academic literature on green and grey infrastructure within residential streets?

3) How is green and grey infrastructure integrated within residential streets?

4) What are the barriers, enablers and considerations for the design and implementation of green and grey infrastructure in streets?

1.2.2 Research Objectives 1) To examine functions and determine the definitions for infrastructure defined as green and grey in the context of residential streets: a) To develop a framework for defining various infrastructure at the street scale b) To investigate what functions the various types of infrastructure serve within a street

2) To investigate what is known about the academic literature on green and grey infrastructure within residential streets, in particular: a) Geographic distribution b) Study settings c) Topics studied d) Disciplinary scope e) Potential relevance of research to practice

3) To investigate the integration of green and grey infrastructure within residential streets: a) To investigate how integration is happening at the street scale b) To investigate which types of infrastructure are integrated

4) To discuss barriers, enablers and considerations for the design and implementation of green and grey infrastructure into suburban streets.

1.3 O R G A N I S A T I O N O F T H E S I S

Chapter 2 provides a narrative literature review on 1) relevant concepts such as green infrastructure and landscape services, 2) history of residential streets and 3) current knowledge such as known barriers to implementation. Chapter 3 describes the research design and methodology. Chapter 4 describes the results of the review Chapter 5 discusses key findings in relation to the research questions. Chapter 6 concludes with some suggestions for future research.

L I T E R A T U R E R E V I E W

2.1 B A C K G R O U N D

2.1.1 Why is the improvement of streets important? Streets are an integral part of a residential neighbourhood’s urban and social fabric; they are places where people walk, socialize and where children play (Barnett, 1982; Jacobs, 1961; Krier, 2003; Lynch, 1960; Spreiregen, 1965). They form a stage for the neighbourhood’s public life, and residents often identify themselves by the street on which they live (Girling & Helphand, 1994). Streets are also conduits for traffic (wheeled and pedestrian), parking and a multitude of services above and below the ground (Girling & Helphand, 1994; Spatari, Yu, & Montalto, 2011).

2.1.2 Landscape Services – a shift in the perception of street infrastructure Landscape Services is a framework which has recently stemmed from the widely used and recognised Ecosystem Services Framework (Bastian, Grunewald, Syrbe, Waltz, & Wende, 2014; Termorshuizen & Opdam, 2009). Ecosystem services are defined as benefits that humans derive from ecosystems (De Groot, Wilson, & Boumans, 2002; MEA, 2007). The ecosystem services framework is a tool used to regulate sustainable use of natural resources. First conceived in the 1990’s and developed over the last two decades, the Millennium Ecosystem Assessment (MEA, 2007) has helped to evolve the concept considerably, with internationally-recognized online information guides such as TEEB (TEEB, 2010) making the ecosystem service classification system publically available. However, despite its popularity and frequent application, the concept of Ecosystem Services is still evolving and is not without weakness (Seppelt, Dormann, Eppink, Lautenbach, & Schmidt, 2011). It has been criticized for its lack of focus on the cultural and social aspects as well as its failure to integrate man-made systems and interactions (Valles-Planells, Galiana, & Van Eetvelde, 2014).

The concept of landscape services was created then many researchers found the ecosystem services too restricting, and isolated in its focus on solely natural systems as well as the limited focus on the ‘cultural’ category, making it less appropriate for disciplines that look at urban settlements as an integrated system. In contrast to the commonly used ecosystem services classification systems such as the MEA and TEEB, the landscape services as described by Valles-Planells et al. (2014) has a more balanced distribution of service categories. The classification system developed by Valles-Planells et al. (2014) is the result of a critical evaluation of the five most accepted ecosystems frameworks, which resulted in the addition of several categories that better represent the complex nature of urban environments and the services provided by both natural and man-made systems, all of which support our livelihoods. Urban ecosystems are inherently modified and fragmented, and comprised of a wide array of elements (Gómez-Baggethun & Barton, 2013). Taking this view to the street scale, a suburban street can be viewed as a complex system where a multitude of elements, both natural and man-made, provide a wide variety of functions. The landscape services concept can be a powerful tool in helping us understand and explore the variety of functions complex urban environments provide for human needs.

2.1.3 Historic background of infrastructure The term ‘infrastructure’ has always been commonly defined as ‘the basic systems and services, such as transport and power supplies, that a country or organization uses in order to work effectively’ (Cambridge Dictionary, 2015). This definition would include examples such as a city’s electricity, wastewater, sewage, and road systems. Infrastructure in residential streets provides vital, yet very specific services (wastewater regulation, transport movement, electricity provision etc.), which are single-function human-engineered systems. When movements such as the ecosystem services concept were advanced (MEA, 2007), they championed an increased understanding of the multiplicity of essential services that natural systems provided to humans. Added to primarily human-engineered systems, this understanding expanded the concept of infrastructure to include a wider range of elements than those that have been historically included into the definition.

2.1.4 Defining green and grey infrastructure in streets Although the term Green Infrastructure first appeared in planning discourse in mid 1990’s, it was often used to describe planning approaches which have already been utilized for some time (Wright, 2011). Benedict and McMahon were among the first authors to define ‘Green Infrastructure’ (see Table 1.1 below). Many authors have since defined the term, and its definition has been a somewhat contested topic (Davies et al., 2006; Matthews, Lo, & Byrne, 2015; Mell, 2012; Wright, 2011) with a myriad of alternative descriptions provided at a variety of spatial scales. The table below shows some of the most widely referenced definitions of Green Infrastructure in the past decades.

Author (year) Definition Benedict and McMahon Green infrastructure is an interconnected network of waterways, wetlands, (2006) woodlands, wildlife habitats and other natural areas; greenways, parks and other conservation lands; working farms, ranches and forests; and wilderness and other open spaces that support native species, maintain natural ecological processes, sustain air and water resources and contribute to the health and quality of life for (American) communities and people. Kambites and Owen Green infrastructure is taken, therefore, to encompass connected networks of (2006) multifunctional, predominantly un-built, space that supports both ecological and social activities and processes. Tzoulas et al. (2007) It can be considered to comprise of all natural, semi-natural and artificial networks of multifunctional ecological systems within, around and between urban areas, at all spatial scales. Ahern (2007) Green infrastructure is an emerging planning and design concept that is principally structured by a hybrid hydrological/drainage network, complementing and linking relict green areas with built infrastructure that provides ecological functions United States An adaptable term used to describe an array of products, technologies, and Environmental practices that use natural systems - or engineered systems that mimic Protection Agency natural processes - to enhance overall environmental quality and provide utility services. As a general principal, Green Infrastructure techniques use soils and (2014) vegetation to infiltrate, evapotranspirate, and/or recycle stormwater runoff.

Table 2.1.4 Commonly referenced definitions of Green Infrastructure

Benedict and McMahon refer to Green Infrastructure from a balanced perspective (both anthropocentric and eco-centric), essentially describing it as an inter-connected open space system that a) supports ecological processes and b) sustains human life. Kambites and Owen, who defined

Green Infrastructure in the same year, present a similarly balanced view to Benedict and McMahon in that Green infrastructure is a network, and supports both ecological and social activities and processes. They also, however, specifically mentioned in their definition that this network is multifunctional. Tzoulas et. al. (2007) viewed green infrastructure from a much more eco-centric perspective, their definition focusing more so on the natural or artificial systems and their connectivity. Their definition, much like that of Kambites and Owen, mentioned to the multifunctionality of green infrastructure. Tzoulas et. al. also alluded to green infrastructure as separate from the built form, more so as something which is superimposed into, between or around urban areas. Despite some differences, all three of the above definitions view Green Infrastructure at a broad planning scale as a connected system of open space and ecological systems which support human life.

Ahern discussed Green Infrastructure in a much more specific sense that the three previous authors, describing it not as a network but as a planning and design concept, alluding to a rather specific hydrological and drainage functions, as well as the more general provision of ecological values. The United States Environmental Protection Agency (USEPA) defines green infrastructure even more specifically, describing it as products and technologies that mimic natural processes. Aside from Tzoulas et.al. (2007), none of the above authors allude to the man-made or artificial nature of some green infrastructure in their definitions. USEPA also describe green infrastructure as a concept used to primarily address drainage issues, displaying a hydrological focus similar to that of Ahern; but more targeted and at a finer scale. While this these differences in definitions could be due to the varying scale of focus of the different authors, it shows the breadth and ambiguity of the term ‘Green Infrastructure’ in various planning contexts.

While several authors argue that the lack of a clear definition of Green Infrastructure has detrimental effects on its successful implementation (Matthews et al., 2015; Sandström, 2002), it has also become evident that a singular definition for all scales in not possible or helpful for such a broad and multi-disciplinary term (Mell, 2012; Wright, 2011). Both authors, however, agree that clearly defining the terms within specific contexts is an important step of clearly understanding the built environment of a project and it’s goals. The more recent use of the term ‘green infrastructure’ to describe vegetated stormwater management systems such as bioswales and rain gardens (United States Environmental Protection Agency, 2014) reflects current concerns with respect to water, however it restricts the term to defining only one type of infrastructure element and only a few functions.

In contrast to green infrastructure, the term ‘grey infrastructure’ is only mentioned within academic literature when scholars are attempting to define green infrastructure and how it relates to conventionally defined infrastructure. Within this context, the term ‘grey infrastructure’ is most commonly used to define all other infrastructure that is not visually ‘green’ or living. The physical composition and appearance of an infrastructure element (a physical element/component within a street setting) is often a major contributing factor to how members of the public, as well as practitioners and politicians choose to classify it. However, as described by Mell (2012), using appearance alone to classify infrastructure can prove inaccurate when dealing with elements that appear artificial or are partly man-made, even if their function is to support biodiversity or mimic natural processes. Without a clear classification system, a purely visual assessment of components can be subjective, especially when dealing with hybrid infrastructure elements such as rain gardens.

Mell (2012) suggests that the subjectivity of this approach can often lead to ambiguity and vagueness in communication amongst the various stakeholders and disciplines involved in implementing green infrastructure projects. In response to these considerations, Davies et al. (2006) have proposed a way of categorising infrastructure elements using a continuum that identifies whether infrastructure elements can be identified as more ‘green’ or ‘grey’ in a particular setting.

Figure 2.1.4 The Green-Grey Continuum created by Davies et al. (2006)

Each infrastructure element’s components (living or man-made) are analysed against it’s function (benefitting humans or ecological systems), and depending on a combination of these factors the infrastructure element is placed along the continuum. Davies’ approach is valuable in that can be used at a multitude of scales. The inclusion of both components and functions in defining infrastructure elements provides a more balanced view when defining what is green infrastructure and what is grey. Unfortunately, Davies’ (2006) method of defining green and grey infrastructure is still subjective in part. In Davies’ study, workshop participants decided which functions of elements would be attributed to green infrastructure and which to grey. At the street scale, there is still a lack of a clear and replicable system for defining green and grey infrastructure.

2.2 R E S I D E N T I A L S T R E E T S T H R O U G H H I S T O R Y

A street is commonly defined as ‘a road in a city or town that has buildings that are usually close together along one or both sides’ (Cambridge Dictionary, 2015). In this thesis, the boundary of a street is defined by the legal boundaries of the adjacent property, and includes everything within the legal street boundary (also known as ‘right of way’ or ROW); including grassed or planted berms, sidewalks and sometimes encroaching fences. Adjacent buildings are not included as components of the street in this research. The streets of interest in this research are those located in first-world countries, including the U.S., Canada, Australia, New Zealand and several European countries. Third- world countries were excluded from this review due to the marked difference in development patterns.

2.2.1 Roman streets The very first street standards appeared in Rome in 15 B.C., where streets were around 4.5 m in width with a 2.2m carriageway in the centre, and raised symmetrical sidewalks either side (figure 2.1). According to Southworth and Ben-Joseph (2003), these streets were hard paved surfaces bordered closely by building facades and often partially enclosed with arcades to provide shelter for pedestrians. There were no trees or plantings present in these narrow city streets, and their primary function was to provide safe passage for pedestrians and animal-drawn carts carrying goods. The

6 general section of these city streets, although often simplified, can also be seen in many medieval cities.

Figure 2.2.1 Typical section of a 15 BC Roman city street based on Southworth and Ben-Joseph (2003).

Table 2.2.1 Landscape services provided by 15 BC Roman city streets

The lack of technological advancements and requirement to accommodate over-ground and underground services at the time of construction means there was less pressure to provide extra space for these, allowing the streets to remain relatively small in scale for centuries. These streets in historic centres today create successful pedestrian-oriented environments which support social interaction, and have been found to contribute to liveable and vibrant neighbourhoods by a number of influential urban design theorists (Dover & Messengale, 2013). The small scale and simplicity of these streets also meant that they were often riddled with congestion and sanitation problems, as there was often a lack of effective drainage or sewerage (Southworth & Ben-Joseph, 2003). Although the intimate scale of these streets has been known to provide a comfortable and attractive pedestrian environment, in many countries today the replication of these streets of such scales may be difficult or inappropriate due to various spatial requirements such as minimal required widths of vehicle carriageways and footpaths, the need for utility strips and emergency vehicle access.

2.2.2 First suburban streets Long after the Roman streets, the first planned English suburban neighbourhoods started to develop their own unique street typologies in the late eighteenth century (Southworth & Ben-Joseph, 2003). The architects designing such neighbourhoods experimented with a variety of street widths and configurations, both in England and the United States. The early developments were populated by

7 the elite social classes, and had very wide streets designed for smooth carriage rides. They provided a pleasant contrasted to the pollution and congestion of the city streets of the era (Southworth & Ben-Joseph, 2003). Commissioned in 1904 London, Hampstead Garden was the first suburb designed for a mix of social classes, and the first to actively include cul-de-sacs into its planning. With the arrival of the motorcar partway through the suburb’s conception, the designers predicted that creating several cul-de-sacs which were connected by a pedestrian network would be a good way to ensure the residential streets remain quiet and liveable in the times to come. Southworth and Ben- Joseph (2003) describe Hampstead Garden as one among the first suburbs to develop smaller-scale streets, although these were still much wider than old Roman streets.

Figure 2.2.2 Typical section of original street in Hampstead Garden based on Southworth and Ben- Joseph (2003).

Table 2.2.2 Landscape services provided by the original streets of Hampstead Garden

The streets had gravel surfaces and featured no curbs or spatial separation between vehicle and pedestrian movement. They were lined with trees set within grass verges, and were bordered by low fences and facades of dwellings (Southworth & Ben-Joseph, 2003).

2.2.3 First suburban streets retrofitted for contemporary use With the arrival of the private motorized transport, the streets of Hampstead Garden and many other old suburbs evolved to accommodate more and more functions. Various infrastructure elements accommodating these functions have been retrofitted into the existing street profile, with the right-of-way widening only minimally. Although garaging and on-street parking are not readily

8 accessible to all residents as they would be in a typical post-war suburb, Hampstead Garden remains one of the most desirable places to live in London.

Figure 2.2.3 Typical section of updated street in Hampstead Garden based on Southworth and Ben- Joseph (2003).

Table 2.2.3 Landscape services provided by the retrofitted streets of Hampstead Garden

Although the streets of Hampstead Gardens have been adapted to cars over the last century, they have largely retained their relatively small spatial scale and abundant vegetated elements. While the pervious cover of the streets has been reduced from the original streets of the 1900’s, they have also been retrofitted to serve an increased number of landscape services required by modern lifestyles.

2.2.4 Residential streets of the private car era The increasing availability of automobiles has gradually changed society’s expectations and demands for the way streets were designed in cities (Karndacharuk et al., 2014), with efficient traffic movement being commonly seen as their primary function. Streets became wider, harder and increasingly complex, becoming conduits for faster and heavier traffic as well as effective conveyance of underground and overground services necessitated by surrounding development (Girling & Helphand, 1994). The spatial separation of wheeled and pedestrian traffic also became more important for safety reasons. As suburban development became promoted in the US in the 1930’s,

9 the first standardized suburban design development principles emerged, including street design standards, that became the foundations for most post-war suburban streets (Southworth & Ben- Joseph, 2003).

In the United States, the widths of vehicle carriageways built in the 30s and 40’s varied from of about 6.7-12 meters with curbs either side, a planting/ utility strip, a footpath (although optional) and trees planted along the property edge of the footpath. In colder climates with heavy winter snowfalls, even more room was allocated to create appropriate clearance between cars, space for storage of snow and for the safe passage of snow ploughs (ASCE, NAHB, & ULI, 1974). Trees and verges were used primarily as a decorative element in the street. The trees, which were historically placed between the footpath and the road, were now being placed between the footpath and the adjoining property. This was because the removal of vertical elements alongside the carriageway was believed to reduce the severity of minor crashes.

Figure 2.2.4 Typical section of post-war suburban street based on Southworth and Ben-Joseph (2003).

Table 2.2.4 Landscape services provided by post-war suburban streets

The pedestrian space within suburban streets became unsafe and unattractive due to a designed dominance of vehicle movement (Dover & Messengale, 2013; Girling & Helphand, 1994; Southworth & Ben-Joseph, 2003). The pedestrian space became barren, unhospitable, and often unsafe. At the time of design, it was believed that making the task of driving easier through removing potential 10 obstacles and increasing road width made it safer (Dumbaugh, 2005). However, large road widths are now known to be one of the main factors in car accidents occurring on residential streets (Dumbaugh & Rae, 2009; Gårder, 2004; Leaf, Preusser, & United, 1999; Rosén, Stigson, & Sander, 2011).

In recent years, the excessive width of suburban streets has also been linked to car dependence, and a decrease in the use of other, more sustainable modes of transport (Dumbaugh & Li, 2010; Gårder, 2004; Leaf et al., 1999). Environments designed primarily for car use were based on the assumption that the residents could maintain ownership of a vehicle; disregarding that limited access to a motor vehicle or public transport could result in social isolation (Dobson & Sipe, 2008). Garceau et al. (2013) found that car dependence was correlated with increased human obesity due to physical inactivity, as most walking-distance journeys were now being taken by car. Cars are also considerable generators of air pollution in cities, a major contributor to illness and death, particularity during heat waves (Kim, Deo, Chung, & Lee, 2015). Furthermore, carbon dioxide emissions are a significant contributor to climate change.

The increased width of streets and associated sprawling development also meant a significant increase of impervious cover (mainly asphalt), which has been widely accepted to contribute to increased stormwater run-off (Jennings & Jarnagin, 2002), urban flooding (Liu, Chen, & Peng, 2014) and significant reduction in water quality of nearby waterways (Carle, Halpin, & Stow, 2005). The traditional stormwater management systems designed to collect and convey is often unable to cope with increased rainfall volumes, resulting in overflows and significant water pollution. The inclusion of trees and other vegetation into the public right-of way was primarily for decorative purposes, and the space dedicated to these elements was not sufficient to offset the high impervious cover of a street.

2.3 R E T R O F I T T I N G

2.3.1 The case for retrofitting post-war suburbs Retrofitting means installing elements that were not available during the original installation (Dunham-Jones & Williamson, 2009). Over the years, the post-war suburbs created a double-edged sword – an unsustainable housing typology favoured by the residents and sprawling areas of out- dated and car-dependent infrastructure (Forsyth, 2012; Girling & Helphand, 1997; Moos & Mendez, 2014).

Ageing housing stock and infrastructure has caused a gradual migration of residents from post-war inner-ring American suburbs to either the city or to new outlying developments in several American cities which started in the 1990’s (Lee & Green leigh, 2005). This trend has been described by a number of authors (Cooke, 2013; Després et al., 2004; Forsyth, 2013), as inner-ring suburbs are left vulnerable to financial downturn (Cooke, 2013), increases in poverty and crime (Lee & Green leigh, 2005) and crumbling infrastructure (Church, 2014). The re-introduction of multiple landscape services (functions) into streets of dilapidated neighbourhoods using retrofits is not new; it is a valuable approach to reviving auto-centric suburban and ex-urban sites (Dover & Messengale, 2013).

2.3.2 Retrofitting suburban streets Street retrofits that are focused on calming traffic and enhancing the social life of streets are numerous (Karndacharuk et al., 2014), as are studies of street elements aimed at improving natural drainage, biodiversity value or aesthetics (Church, 2014; Joan Iverson Nassauer, 2011; Joan Iverson Nassauer, Wang, & Dayrell, 2009; Nickel et al., 2013).

At the street scale, one of the first movements to improve residential streets in the era of the motor car was conceived in the late 1950’s, with Colin Buchanan’s idea of shared streets, where traffic was slowed by various design elements and pedestrians could co-exist safely with cars. The design of shared streets looked to actively increase the dominance of the pedestrian within a residential street, while creating a safe and attractive environment that still accommodated slow movement of vehicles. The idea has been widely adopted and developed in the Netherlands as ‘woonerven’ (Karndacharuk et al., 2014) and in several other European countries since its early conception. In first-world countries struggling with vehicle dominance, variations of similar ideas such as traffic calming (UK 1970’s, US 1980’s), Living streets (International), Local Area Traffic Management (NZ), and Home Zones (UK) have also been widely adopted by engineers, urban planners and regulatory agencies from the 1970’s onwards. These ideas are commonly applied to street retrofit projects.

In more recently designed residential and suburban streets, it is common to see reduced street widths (Southworth & Ben-Joseph, 2003) in an attempt to slow traffic, as well as the inclusion of vegetated elements such as open stormwater treatment systems (National Association of City Transportation Officials, 2013), designated wider pedestrian footpaths and often cycle paths. Retrofitted streets often display some of these features, with LID (low impact development or open vegetated stormwater systems) retrofits being relatively common in North America. The best- practice street retrofit shown in figure 2.5 is loosely based on illustrations by Southworth and Ben- Joseph (2003). While this example includes both hard traffic calming elements and vegetated stormwater filtration elements, it is uncommon for retrofit projects to focus on both aspects simultaneously, and little is known about the level to which integration of green and grey infrastructure elements takes place within new and retrofitted street corridors.

Figure 2.3.2 Section elevation of best practice suburban street retrofit based on Southworth and Ben- Joseph (2003).

Table 2.3.2 Landscape services provided by best practice suburban street retrofit

The use of green infrastructure elements within street designs has been found to provide more landscape services than the traditional singular decorative role of street trees and planting. The inclusion of vegetated stormwater elements and permeable pavements in street designs has been increasingly used to address stormwater issues (Ahiablame, Engel, & Chaubey, 2013; Qin, Li, & Fu, 2013) whilst also increasing biodiversity in neighbourhoods (Kazemi, Beecham, & Gibbs, 2011). The use of trees and planting has also been shown to reduce air pollution and sequester carbon (Kiss, Takács, Pogácsás, & Gulyás, 2015), as well as providing climatic comfort (Coutts, White, Tapper, Beringer, & Livesley, 2015).

It has also been found that a decentralized approach to stormwater treatment using elements such as swales, rain gardens and tree filter boxes can be an effective way to alleviate pressures on 13 traditional water infrastructure, while removing harmful pollutants from impervious-surface run-off (Chapman & Horner, 2010; Qin et al., 2013). The inclusion of well-designed vegetated elements within a street has also been linked to improved aesthetics (Church, 2014), increased property value (Brander & Koetse, 2011; Kong et al., 2007), a stronger sense of custodianship among residents (Church, 2014) and the ability to sequester atmospheric carbon (Yang, McBride, Zhou, & Sun, 2005).

Encouraging more active modes of transport such as walking and cycling through street design can result in improved mental and physical health of residents (Badland & Schofield, 2005; Van Dyck, Cardon, Deforche, Owen, & De Bourdeaudhuij, 2011), increased social capital (Bain, Gray, & Rodgers, 2012; May et al., 2008) improved street and neighbourhood safety (Mueller et al., 2015) and reduced automobile crash rates (Dumbaugh, 2005). The decrease in inactive and sedentary lifestyles linked to car-dependence has been found to have a positive effect on government expenditure on healthcare (Annear, 2008). Less cars on the streets means less toxic exhaust emissions, which, in turn, leads to cleaner air (May et al., 2008), and reduced numbers of vehicles means less reliance on fossil fuels for everyday livelihoods, coupled with greater resilience in times of wavering fuel security (Badland & Schofield, 2005; Garceau et al., 2013).

Table 2.3.3 Landscape services provided by streets through time

Figure 2.3.4 Evolution of residential street layouts through history. Indicative plans based on Southworth and Ben-Joseph (2003). Scale varies (see dimensions).

Over the centuries, residential streets have grown in scale; and evolved to become complex systems that serve a much wider range of functions than the very first roman streets. Streets have become increasingly complex through time. Many streets built today still have the same general profile as the post-war suburban streets of the 50’s, although many contemporary developments are building these to narrower widths.

Figure 2.3.5 Indicative plans of typical suburban street and a best - practice suburban street retrofit based on Southworth and Ben-Joseph (2003). Not to scale.

The contemporary best-practice retrofitted street strives to perform more functions than streets have ever done historically, whilst fitting into the same or at times smaller right-of way than the suburban streets of the post-war motor age. With the advance of research, technology and well- applied design, street retrofits have the capacity to address the social, cultural and environmental problems brought on by previous unsustainable development patterns.

2.4 D E S I G N A N D I M P L E M E N T A T I O N

2.4.1 Known barriers to implementing infrastructure in streets At the city planning scale, Tjallingii (2003) and Svendsen, Northridge, and Metcalf (2012) explore the tension between ‘grey’ infrastructure (referred to as red infrastructure by Tjallingii) such as roading and housing; and ‘green’ infrastructure (forestry, parks, nature conservation, agriculture) within urban and semi-urban contexts. Tjallingii describes the tendency for Green planning advocates to take defensive and even offensive approaches to securing room for green space development. This trend is explained as being primarily due to a lack of space in cities, with ‘green’ structure planning often being dominated by ‘red’ infrastructure. Tjallingii speculated that this was often due to red structure carrying the promise of economic gain. Svendsen et al. (2012), Sandström, Angelstam, and Khakee (2006) and Sandström (2002) describe a similar pattern, where grey infrastructure is so often favoured over green infrastructure when planning decisions are made.

Two of the major reasons for the lack of prioritization of green infrastructure are definition ambiguity and a pattern of path dependence amongst governments (Matthews et al., 2015; Sandström, 2002). Path dependence relates to the tendency of governments to continue doing things the way they have been done, and a reluctance to integrate new knowledge and change processes. Several researchers describe a lack of definition clarity and understanding of green infrastructure within government documents as one of the biggest barriers to the implementation of green schemes at the city scale (Matthews et al., 2015; Wright, 2011).The definition ambiguity has, in many ways, led to a re-labelling of existing open space as ‘green infrastructure’ and, in turn, has resulted in many governments precluding the development of truly functional, integrated and connected green infrastructure planning and implementation (Sandström et al., 2006). Olorunkiya, Fassman, and Wilkinson (2012) also suggest that much of the uncertainty in relation to green infrastructure has been due to a lack of understanding and knowledge of its effectiveness.

Streets with increased landscape services require input from a multitude of disciplines, and trade- offs between functions. This makes the design process complex as many divisions within municipalities operate independently from each other, making it difficult for them to design successful streets in a collaborative way (Després et al., 2004; Karndacharuk et al., 2014). Aside from this, the pressure to address a variety of problems often comes at a cost (Forsyth, 2005) and the task of accommodating a multitude of functions and elements within a space which cannot be too large can create formidable design challenges (Bain et al., 2012). Despite the above issues discussed by a number of authors, it is unclear what comprises the most commonly encountered barriers during the design and implementation of green and grey infrastructure at the street scale. A thorough analysis of the key barriers to the design and implementation to various infrastructures in streets could lead to a better understanding of how these barriers could be overcome.

2.4.2 Enablers to implementation of multiple landscape services While exploring the tensions between green and grey infrastructure at the city scale, Tjallingii (2003) discussed another approach. This involved green structure planning potentially acting as an integrating force, working with grey structure planning initiatives to ensure both are accommodated in symbiotic ways through a continuing dialogue of the various planning sectors and agents who often do not communicate as policy planning and development takes place. In his essay about retrofitting declining first-ring suburbs, Després et al. (2004) describes a similar need for inter-

16 disciplinary dialogue to take place. Within the street context Karndacharuk et al. (2014) describes a similar idea, expressing the need for multiple professions involved with the creation, renewal and maintenance of streets to work collaboratively in order to create well-integrated street designs. Collaborative multi-disciplinary approaches to design, could be a key step to the successful design and implementation of more landscape services into streets.

At the street scale, the use of green infrastructure functions to serve the purpose of traditional stormwater infrastructure has been proven effective (Nickel et al., 2013), meaning that over time government expenditure of extensive replacements of underground stormwater pipes could be reduced (Knight, 2003; Nickel et al., 2013). This, coupled with better connectivity and reduced reliance on traditional stormwater infrastructure, has the potential to increase the resilience in times of crisis; and reduce the increasing effects of climate change on human settlements (Matthews et al., 2015). Thoughtful planning and integration of green and grey infrastructure could bring opportunities to enhance the functionality of both types of infrastructure at the street scale. It is currently unclear if integration of green and grey infrastructure is occurring, and gaining an understanding of the level and types of integration could shed light on whether integration could be used as a potential enabler to building better streets. It is still unclear what other enablers to the implementation of green and grey infrastructure are encountered at the street scale.

2.4.3 Status of the literature on green and grey infrastructure in streets

In order to investigate the levels of implementation and advancement of green and grey infrastructure in residential streets, it is important to know how the research on the topic of translates into practice, as well as what disciplines are undertaking the research and what the local climatic conditions might be. In their research about the relation of academia and practice of the Landscape Architecture profession, Milburn and Brown (2016) alluded to the fact that academic researchers and practitioners had very different views about what topics were most valuable to research. Most practitioners’ views leaned toward the importance of sustainable design, water management, construction, ecology and plant materials, while the academics producing the research mostly produced studies of theory, history, education, perception and case studies. It is yet unknown what topics are most commonly studied within research on green and grey infrastructure in streets.

M E T H O D S

3.1 R E S E A R C H D E S I G N

This thesis used both narrative and systematic literature review methods in order to answer the research questions. A narrative literature review was used to define the general breadth of research on the topics, provide preliminary definitions and generate search terms. A systematic literature review was then carried out to answer the research questions.

3.2 N A R R A T I V E L I T E R A T U R E R E V I E W

A broad review of the history and preliminary definitions of key terms such as ‘green Infrastructure’, ‘grey Infrastructure’, 'street' and ‘retrofit’ were completed in order to scope the broad status of the literature and to generate search terms. As definitions and relevant elements were recorded, they were added into the list of relevant search terms that were later used to systematically search the academic literature.

Grey infrastructure in streets was preliminarily defined as ‘sidewalks, street characteristics, pedestrian crossings, and traffic signals’ based on (Boarnet, Forsyth, Day, & Oakes, 2011) definition of street infrastructure, as well as ‘the network of underground utilities that serves our towns and cities’ (Hao et al., 2012). Green infrastructure in streets was preliminary defined as ‘all natural, semi- natural and artificial networks of multifunctional ecological systems within, around and between urban areas, at all spatial scales’ (Tzoulas et al., 2007). Synonymous words for green and grey infrastructure and street elements were located both within the relevant literature and through the use of Internet searching. As various countries use different terms, these were added to a list of keywords to ensure they were geographically inclusive.

For the critical review of streets throughout history, the Landscape Services Framework developed by Valles-Planells et al. (2014) was used. Further information about the categorization can be found on page 3 and in their detailed paper about landscape services categorization. Functions which various streets accommodated were distributed into categories outlined by Valles-Planells et al. (2014), and compared against one another to gain an overview of how the functions streets provided changed throughout history. The functions provided by streets which were described in various supporting literature were put into tables in order to summarise and create an overview. This list is not exhaustive; and in order to become so, would need its own extensive and large-scale systematic literature review. The table below explains the various Landscape Service categories outlined by Valles-Planells et al. (2014).

R E G U L A T I N G & P R O V I S I O N I N G M A I N T E N A N C E C U L T U R A L & S O C I A L

Nutrition Regulation of wastes Health

Terrestrial plant and animal foodstuffs Bioremediation Mental health

Freshwater plant and animal foodstuffs Dilution and sequestration Physical health

Marine plant and animal foodstuffs

Potable water

Material Flow regulation Enjoyment Biotic materials Air flow regulation Passive enjoyment Abiotic materials Water flow regulation Active enjoyment Mass flow regulation

Energy Regulation of physical environment Self-fulfilment (Personal)

Renewable biofuels Atmospheric regulation Way-finding

Renewable abiotic energy sources Water quality regulation Scientific resources

Pedogenesis and soil quality regulation Didactic resources

Spiritual experience

Source of inspiration

Daily activities Regulation of biotic environment Social fulfilment

Place to live Lifecycle maintenance and habitat protection Social interactions

Place to work Pest and disease control Place identity

Place to move Gene pool protection Sense of continuity

Regulation of spatial structure

Connection of spaces

Buffer disturbing use

Provision of spatial complexity of the place

Table 3.2 Landscape Services Classification as proposed by Valles-Planells et al. (2014)

3.3 S Y S T E M A T I C L I T E R A T U R E R E V I E W

Systematic literature reviews are a widely used method for answering specific questions that need unbiased synthesis of large quantities of literature in order to ensure accuracy of the findings (Cochrane Collaboration, 2011; Gough, Oliver, & Thomas, 2012; Petticrew & Roberts, 2006).

A traditional non-systematic, or narrative, literature review is used to explore the background information for a study, provide expert summaries or present an argument; however, as a research method it is considered too narrow in scope and too biased in viewpoint to meet existing standards of scholarly research (Gough, Oliver, & Thomas, 2013; Petticrew & Roberts, 2006). In contrast to a non-systematic (narrative) literature review, a systematic literature review is a scientific tool used to summarize and appraise unmanageable quantities of research through the adoption of a particular replicable methodology with the overall aim of producing an unbiased scientific summary of the evidence (Collins & Fauser, 2005; Petticrew & Roberts, 2006).

Increasingly, policy-makers and politicians are using evidence based on systematic literature reviews as a basis for their decision-making (Gough et al., 2013; Petticrew & Roberts, 2006; Ridley, 2012). A 19 systematic review’s ability to find, appraise and synthesize evidence (Cochrane Collaboration, 2011) as well as the comprehensiveness of the overview (Gough et al., 2012) is necessary in order to examine and define green and grey infrastructure within the residential street context internationally, as well as to identify any barriers and enablers to design and implementation. The explicit and reproducible methodology, along with thorough relevance appraisal, result in minimized bias (Cochrane Collaboration, 2011), enabling a clear evaluation of the current findings about green and grey infrastructure based on relevant peer-reviewed scholarly literature.

While it could be argued that a method such as stakeholder, government official or expert interviews would answer many of the research questions of this study, this method would carry a greater risk of bias, a lack of clarity on the nature of the evidence and very limited international relevance (Gough et al., 2012). There is also currently no synthesis of existing knowledge available on the topic.

The following structure of a systematic literature review uses the principles outlined by internationally recognized and reputable sources specializing in systematic literature reviews, including the Cochrane Handbook (Cochrane Collaboration), the Campbell Collaboration, EPPI and SCIE (Ridley, 2012).

3.3.1 Inclusion criteria

Articles were selected for review on the following criteria: 1) studies that investigated built green or grey infrastructure, 2) within a residential street context, 3) peer-reviewed Anglophone academic journal articles, 4) from developed countries. No time restrictions were applied in order to identify temporal shifts in the literature. Literature on grey and green infrastructure that was not studied or described within a street setting was excluded as this was outside the scope of the study. ‘Grey literature’ such as conference proceedings and theses was excluded from the review.

The original papers targeted for review were evaluations of implemented green, grey and green-grey infrastructure retrofit projects. Due to insufficient findings, the research questions were expanded and inclusion criteria for papers were amended to include non-retrofit studies of green and grey infrastructure within residential street contexts.

Research topic The papers to be included in the review were restricted to studies that focused on the design, implementation and management of green, grey and green-grey infrastructure that was already built (i.e. case studies). Un-built projects and theoretical frameworks were excluded as these were outside of the scope of the review.

Street context The original scope of the study was restricted only to suburban residential street retrofits in order to gain knowledge specifically within this context. Due to limited findings the scope was expanded to include residential streets within urban and suburban settings. Studies that focused on green or grey infrastructure elements outside the street context were excluded as this was outside the scope of the research. Papers that evaluated streets without any specific focus on one or several infrastructure elements were also excluded. 20

Type of literature Only peer-reviewed academic journal articles were included in this review. The peer-review process assures a high quality of information and defensible evidence is provided (Ridley, 2012). Books, websites, government policies and grey literature as defined by Ridley (2012) (including reports, theses and dissertations, conference literature, media reports, research in progress, leaflets and posters, patents, letters and diaries) were excluded from the review. These types of literature do not always go through a rigorous quality appraisal, meaning that there is a risk of bias, inaccurate information and lack of evidence supporting the authors’ statements. Due to the multi-disciplinary scope of the research questions, no specific academic journals were chosen at the time of searching in order to include the largest amount of relevant peer-reviewed articles possible. The academic journals generated by the searches were recorded in the screening phase of the systematic review process.

Country of origin The original study boundaries included only English-speaking new-world countries due to their distinct development patterns and suburban form. However, due to very limited results, this was expanded to include all first-world countries in order to gain valuable insight from various suburban and urban street environments. Studies from third world countries and developing countries were excluded, as their urban development patterns, economic conditions and population density in suburbs vary too greatly from developed countries.

Publication year Initially, the time of publication for relevant papers was restricted to the last 10 years of study (papers published between 2005 and 2015). Due to limited findings, the earliest year of publication was removed to include the earliest articles available in the selected electronic databases (varied with database’s default settings), while the latest year remained 2015 as this was when the searching was completed (December). The lack of earlier time restrictions enables the reviewer to make note of the shifts, and emergence of, new topics within the research through time.

3.3.2 Searching strategy

Search terms The narrative review carried out to scope the body of literature and generate definitions was also used to generate relevant keywords. As definitions of key terms were developed, a list of the relevant functions, elements and synonymous words were added to the definitions. This helped to generate a sufficient number of keywords to extensively cover relevant research topics. This process also helped to determine which areas the study would be restricted to, as well as to determine which search engines generated the most relevant results. The keywords used for the search can be found in Appendix A.

In each database, combinations of the search terms, using wildcard terms and truncations where appropriate, were applied. For instance, the search string for a Science Direct was: ((“footpath” OR

“pave*” OR “sidewalk”) AND (“street” or “road” or “right-of-way” or “carriageway”) AND (“retrofit” or “repair” or “resurface” or “renewal” or “upgrade”)).

As the search process evolved and the inclusion criteria were amended, a number of initial searches were repeated to fit the new inclusion criteria to eliminate the risk of missing relevant articles through the use of a superseded narrow scope.

Databases Searching for relevant data was conducted using a range of reputable research databases that met international standards. The databases focused on scholarly literature within a variety of disciplines (including environmental, ecological and public health) to ensure a comprehensive and unbiased sample of relevant high-quality academic literature was obtained. The following databases were used: Science Direct, Scopus, Web of Science, Avery and JSTOR. The Lincoln University Library Database Search Engine (which covers over 150 national and international databases) was used to ensure no results from other potentially useful databases were missed.

Search method testing After the first few searches generated a number of relevant articles (articles that met the selection criteria in section 3.4.1), a selection of keywords recorded within the three selected articles were tested in the six databases to ensure the databases responded to the keywords. Relevant articles came up in all instances of this exercise, proving the searching methodology effective.

Stopping the search The logic for stopping the systematic review described by Petticrew and Roberts (2006) was applied. The search was stopped once duplicates of previously downloaded citations dominated the search results.

Screening Initial screening was carried out through the searching process by scanning through the titles of all search hits for relevant papers. References captured through the searching process were imported into an Endnote library and duplicates were removed. The inclusion criteria were applied to each article in order to eliminate any irrelevant articles from those captured by the search. In the first instance, the inclusion criteria were applied to the title only in order to efficiently remove clearly irrelevant articles. Remaining articles were then further filtered by abstract and full text where appropriate. This generated a more refined number of articles that met the initial inclusion criteria. Once the selection criteria were applied to the screened papers, 34 were identified as relevant and were processed using the steps in the section below.

3.3.3 Method for processing papers

Firstly, the literature was mapped using an excel spreadsheet. The same spreadsheet was then used to critically appraise the literature. Once critically appraised, Nvivo was used to code relevant sections within the literature. The findings were then synthesized into excel spreadsheets which corresponded directly to specific research questions and evaluated.

Mapping the literature Basic information about each study was recorded in an excel spreadsheet. This was done in order to ensure that each article met the final selection criteria, as well as to establish quantitative patterns within the literature needed to answer Research Question 2. The mapping criteria were based on a guide outlined by Gough et al. (2012)

Table 3.3.3 Information recorded during the mapping phase

Critical appraisal Each paper was assessed in accordance to the Weight of evidence approach, described by Gough et al. (2012). Papers were assessed on soundness of study, appropriateness of study design to answer research questions, and relevance of the study’s focus to the review.

Table 3.3.4 Critical Appraisal Criteria based on Gough, Oliver and Thomas, adopted from Torgeson et al. 2008

Only studies rated Medium and High were accepted into the review. Studies rated ‘Medium’ were seen as holding slightly less weight than studies rated ‘High’.

Final application of inclusion criteria Once all of the above information was recorded and articles were critically appraised, the papers were once again evaluated against the final inclusion criteria and any articles that did not fit the criteria were removed. Papers that investigated unbuilt of hypothetical retrofit interventions or street infrastructure were excluded as they were outside of the scope of the review and often not strictly empirical. Papers that used secondary data (such as government documents or existing census data) as the main basis for their methodology (e.g. cost projections) were excluded as they 23 were often not focused solely on streets, nor spatially grounded and therefore did not explicitly meet the location criteria. While they provided interesting insight into some of the wider implications of installing various infrastructure elements and their life cycle costs, they were outside the scope of this review. Papers which developed a framework based on a review of previous literature, and hypothetically tested the framework on a built project were also excluded as these studies were outside of the scope of the review.

Once the final selection of papers was obtained, they were organised into two preliminary groups; retrofits and non-retrofits. In papers that had multiple case studies, any single retrofit study meant the paper was categorised as a ‘retrofit paper’. At this point, 29 papers met the selection criteria for this systematic review (see Appendix B for full list). 15 of these were studies of retrofits within a residential (primarily suburban) street setting, and 14 were non-retrofit studies.

Content analysis and coding Nvivo coding software was used to derive specific information from studies that were relevant to the research questions. The content analysis of the 29 papers is based on an inductive process. A basic hierarchy was created in Nvivo and was expanded and amended as more information was recorded from the articles. The basic hierarchy of findings included the following codes, based on the research questions:

• General study info • Demonstrated landscape services • Definitions • Integration of green and grey • Infrastructure elements discussed • Barriers and enablers

As the coding process took place, the coding hierarchy evolved and was recorded, until a coding protocol was established. A full coding protocol can be found in Appendix C. The studies coded before the protocol was established were coded again using the coding protocol in order to ensure consistency and accuracy of findings.

The information coded in Nvivo was then transferred into excel tables which corresponded to specific research questions, and recorded against the background information of the relevant study.

Quantitative data about the articles such as the year of publication, authorship and geographic location was analysed for temporal, geographical and disciplinary patterns, and was used to answer research question 2 regarding current knowledge about the literature on green and grey infrastructure in streets. Qualitative data recorded for each article using Nvivo was recorded into appropriate excel tables that corresponded to the research questions 1, 3 and 4.

Synthesizing a new framework for defining green and grey Infrastructure Due to a lack of clear definition for green or grey infrastructure at the street scale, a framework for definitions was developed using an adoption of the green-grey continuum presented by Davies et al (2006), instead using the physical components of infrastructure elements in order to classify them as ‘green’ or ‘grey’. The infrastructure elements studied within the multiple papers were recorded and classifies as having a) only natural components (e.g. a tree), only man-made components (e.g. kerb and channel) or a mix of natural and man-made elements (e.g. a vegetated swale). The physical

24 components of the infrastructure elements were assessed and recorded in an excel spreadsheet. This was evaluated against traditional definitions of green and grey infrastructure to determine whether this approach was appropriate for the street scale.

In order to investigate what functions the various infrastructure elements provided within a street, the studied infrastructure elements were classified using the above method, along with the landscape services those infrastructure elements demonstrated in the literature. Any function demonstrated within the literature was coded in Nvivo against the corresponding element (e.g. a swale demonstrated stormwater pollutant removal function). Any functions that were discussed by the authors, but not demonstrated in their research, were excluded. This was done to ensure that the results used for the definitions are empirical and are street-specific. The elements and their corresponding demonstrated functions were then recorded in an excel table. The functions were then organized into three groups using the landscape services framework as described by Valles- Planells et al. (2014). The categories for the functions were Social and Cultural (e.g. accommodating social interaction, educational functions), Regulating and Maintenance (e.g. filtering stormwater), and Provisioning (e.g. providing daily transportation). More detail on the landscape services categories can be can be seen on table 3.2, page 19.

3.5 L I M I T A T I O N S O F M E T H O D O L O G Y

A limitation of systematic reviews, as outlined by Gough et.al. (2012), is publication bias; as it has been shown that studies with no impact are less likely to be published, and that some studies are withheld by those with vested interest in the outcome of these studies. While this is of particular importance within the pharmaceutical industry, it cannot be ruled out that publication bias may also impact some of the studies relevant to this research. There is also a potential bias if the literature is limited to English as outlined by Gough et al. (2012) and Gough et al. (2013). As the searching was carried out using exclusively electronic databases, there is a risk that any relevant articles unavailable electronically were excluded.

R E S U L T S

4.1 D E F I N I T I O N S A N D F U N C T I O N S

4.1.1 Components The chart below includes all of the street infrastructure elements studied in the academic literature within the systematic review. The infrastructure elements are categorised by their composition; green infrastructure being living or nature-made components, green-grey being a combination of living and man-made components and grey infrastructure being strictly man-made components. A clear overlap of natural/living and man-made components is visible below the green-grey infrastructure category.

Figure 4.1.1 Green-grey infrastructure composition chart

This is a simple and effective way to categorize the majority of the elements found within a street. Although through this approach permeable pavement is categorized as strictly grey while it is often referred to as ‘green infrastructure’ (Sansalone, Kuang, Ying, & Ranieri, 2012), this definition method avoids the definition ambiguity that is so commonly linked to green and grey infrastructure.

4.1.2 Functions As described in the Methods section, the landscape services framework was used to categorize every function (landscape service) performed by an infrastructure element that was demonstrated in the literature. Landscape services that were described in the literature, but were not demonstrated, were excluded. The various landscape services are displayed in the table below, and are divided among the three primary landscape services categories. The numbers within each coloured box correspond to the number of papers demonstrating the function.

Table 4.1.2 Demonstrated Landscape services provided by green, grey and green-grey infrastructure elements in the academic literature.

All three infrastructure element categories (Green, Grey and Green-grey) demonstrated landscape services that covered all of the three major categories as described by (Valles-Planells et al., 2014); Cultural and Social (orange), Regulating and Maintenance (green) and Provisioning (blue). Green infrastructure (trees and shrub planting) provided a good variety of social and cultural landscape services, while landscape services in the other two categories were not as strongly represented. Green-grey infrastructure elements appeared to have an equally well-represented variety of landscape services in both the ‘Cultural and Social’ and ‘Regulating and Maintenance’ categories. Only one provisioning function was provided, as demonstrated in two papers. Grey infrastructure elements provided a number of landscape services within all categories, with the most consistently demonstrated service being the enhancement of the pedestrian environment.

4.2 I N V E S T I G A T I N G T H E A C A D E M I C L I T E R A T U R E

4.2.1 Geographic distribution

Table 4.2.1 Geographic distribution, study setting and infrastructure focus of reviewed papers

29 Academic papers on infrastructure elements were published between 1998 and 2015. North America is the most represented country with 12 publications, followed by the UK with 6 papers and Australia with 5. Europe closely follows with 4 publications, and New Zealand has the smallest contribution with 2. Most of the green-grey infrastructure – focused studies have been published in the United States, with the majority of these infrastructure elements performing stormwater management functions. The study of green infrastructure elements is more evenly distributed between the various locations, while the Grey infrastructure-focused literature is primarily published in the United States and in the United Kingdom. Almost two thirds of the papers were located in new-world countries. Over two thirds of the sites studied within the papers were located in suburban settings (69%), with 17.2 % located in both urban and suburban settings and 13.9% in urban settings.

Infrastructure studied Green-grey was the most studied infrastructure type (48.3%) followed by papers that studied a multitude of infrastructure elements with a focus on Grey (27.6%). Green Infrastructure research accounted for 13.85% of the research, green-focused papers (which studied multiple infrastructure types) contributed with 6.9% and Grey Infrastructure was the smallest at 3.5% (table 4.2.4 ).

Climatic Distribution The case studies within the systematic literature review spanned seven climate zones as identified by the Koppen Climate Identification system.

Table 4.2.2 Climatic distribution of literature

The most common climatic conditions of the case studies were Oceanic climates and Humid Subtropical. The precipitation pattern in oceanic climates is often dispersed throughout the year with no particular wet season and frequent cloudy days, along with common storm activity. Humid subtropical climates, where most Grey infrastructure-focused studies were located, have a similarly dispersed rainfall pattern to Oceanic climates, however there is often a summer peak in rainfall. The other climate types had a relatively even dispersal of case studies, also with relatively evenly dispersed infrastructure classifications.

4.2.2 Methods, Research questions and professional affiliation

Authorship and Disciplinary Scope

Table 4.2.3 disciplinary scope of the studies Of the total of 108 authors involved in producing the body of research, the literature was dominated by the environmental engineering profession (25.9%), followed by equally represented Environmental Conservation/Ecology, Biology, Urban Planning, Landscape Architecture and Health 29

Sciences (each contributing 5.6%). Overall, the number of natural sciences researchers is considerably higher (70%) than that of social sciences or mixed sciences researchers (30%). Several papers focusing on perception and use of street elements had a more diverse array of academic backgrounds than of papers studying stormwater management and biodiversity value. The equally represented fields of environmental conservation, biology, urban planning, landscape architecture and social sciences is reflective of the other most studied research questions (table 4.2.4).

Sciences 48.3 % of papers were natural sciences publications (including applied), 41.3% were social science publications and 10.35% were mixed sciences (table 4.2.4).

Table 4.2.4 Sciences affiliation, methods and research questions of reviewed papers

Methods used The most commonly used research method was experimental data collection (34.5%) which was carried out primarily by natural science researchers, followed by mixed social science methods at 24.1% (carried out by social science – based professions) and mixed social and natural science methods at 10.35%.

Research questions studied The research questions and topics within the body of literature could be categorized into 7 groups (table 4.3). Public use and perception of built infrastructure elements (be it green, grey or green- grey) was the most frequently studied question (34.5%). Many of the public perception studies were also linked to aesthetics, and how people perceived the residential street and the infrastructure

30 elements within it. Research questions related to stormwater management efficiencies of green-grey infrastructure elements were the second most studied topic (31%). The third most studied research topic included only 4 studies, and investigated the level of habitat green or green-grey infrastructure provided for fauna.

4.3 I N T E G R A T I O N

The examined literature suggests that there are two types of integration occurring within residential streets. The two types are described below.

4.3.1 Street-scale integration

Figure 4.3.1 Street-scale integration

Street-scale integration occurs where spatially separate elements collectively achieve a common goal. An example of this is a traffic-calming scheme that uses a variety of elements such as strategically placed seats, planters, trees and car parks to achieve slower vehicle speeds. This type of integration is commonly implemented in order to increase pedestrian safety, improve amenity and re-vitalize social life in neighbourhoods.

4.3.2 Element-scale integration

Figure 4.3.2 Element-scale integration

Element-scale integration occurs when a combination of several elements within one space achieves multifunctionality. An example of this is a bioretention swale that also serves as a bump-out (or chicane) to slow traffic. Through an innovative combination of materials and placement, this street element now serves more functions than a swale or a bump-out would serve individually. This type of integration commonly occurred when green-grey stormwater management infrastructure was implemented into streets.

4.3.3 Integration patterns

Table 4.3.3 Summary of integration within the literature

Of the 29 papers included in this review, only 10 papers demonstrated cases of integration of various infrastructure types within a street. The vast majority of integration cases were from literature discussing retrofits, as opposed to non-retrofits. Out of the 10 papers where integration occurred, 6 of the authors explore street-scale integration, with the majority of these authors having an urban design or social science background, and a primarily anthropocentric focus (all but Shu, Quiros, Wang, and Zhu (2014), who evaluated changes in air quality as a product of modal shifts brought about by the studied intervention). Church (2014), another exception, explored cases of element- scale integration, whilst focusing on the cultural and social perceptions of the infrastructure elements. The authors of the three papers that discuss primarily element-scale integration had a strong eco-centric or engineering focus, and came from either ecological or engineering backgrounds.

4.4 B A R R I E R S A N D E N A B L E R S

The barriers and enablers found in the literature were identified as belonging to two groups; actual barriers and enablers and potential barriers and enablers. Actual barriers and enablers were the constraints or enablers that were encountered or demonstrated within the academic literature, and directly affected the successful implementation or design of infrastructure elements. Potential barriers and enablers were the constraints or enablers that were discussed or referenced from other author, but were not a finding of the study itself.

4.4.1 Barriers and Enablers for Green Infrastructure

Figure 4.4.1 Barriers and enablers for green infrastructure

The literature contained only potential barriers and enablers for green infrastructure, all of which were encountered after the implementation of the green infrastructure element (in all cases a tree). No actual barriers or enablers for green infrastructure were found within the literature. An issue of harbouring insect pests forms a potential barrier to the placement of trees within a street, while positive perception of residents is discussed as a potential enabler in both Hunter (2011) and Harvey et al. (2015).

4.4.2 Barriers and Enablers for Green-Grey Infrastructure

Figure 4.4.2 Barriers and enablers for green-grey infrastructure

The actual and potential barriers for green-grey infrastructure elements have a reoccurring theme of spatial constraints, which has been encountered both at the design and management stages of the projects. High costs were also encountered by Page et al. (2015) b at the design stage of the project. All of the green-grey infrastructure studies that encountered barriers were studying stormwater control elements: bioretention cells, basins, rain gardens and a tree box filter. Both Chapman & Horner (2010) and Schlea et al. (2014) found that there was sufficient space for green-grey infrastructure elements within the street; both of these studies being located in suburban areas. Church (2014) speculated that education of residents about the stormwater infrastructure functions could encourage a wider acceptance and therefore positively influence implementation throughout neighbourhoods, while and Page et al. (2015) b noted that cost-effectiveness of various stormwater infrastructure elements could also act as an enabler to their implementation.

4.4.3 Barriers and Enablers for Grey Infrastructure

Figure 4.4.3 Barriers and enablers for grey infrastructure

The most frequently encountered (actual) and discussed (potential) barrier for grey infrastructure elements was the lack of utilization by the residents living nearby. This was an issue for traffic- calming schemes that were dominated by grey elements, but also included several green and green- grey elements as minor parts of the overall street design. High costs were an issue for a removable pavement system trialled by de Larrard, Sedran, and Balay (2013). The only enablers found in the literature were potential enablers, and unlike the ‘barriers’ section, demonstrated some variety. Adams and Cavill (2015) suggested that educating residents about the traffic-calming scheme could potentially increase its utilization, while Biddulph speculated that the success of traffic-calming schemes is dependent on surrounding land use. de Larrard et al. (2013) argued that the long-term cost effectiveness and ease of access for repairs made their removable pavement system a worthwhile investment; while Coulson, Fox, Lawlor, and Trayers (2011) concluded that although residents were slow to utilize the traffic-calmed street directly after installation, the eventual pedestrian use of the street was high.

D I S C U S S I O N

5.1 D E F I N I T I O N S A N D F U N C T I O N S

5.1.1 Definitions The findings suggest that an adoption of the Davies et al. (2006) green-grey continuum based on both structural/visual properties of infrastructure elements is a simple and effective way to categorize infrastructure elements within a street. While describing their green-grey continuum approach, Davies et al. (2006) evaluated which functions provided by elements could be categorized as ‘green’ functions, and which ones as ‘grey’ functions. Given the evident multifunctionality of the studied infrastructure elements within this review, it would be difficult to incorporate landscape services into a clear way of categorizing and defining the various infrastructure elements. Given that many authors define green infrastructure as elements which mimic or assist natural processes (Benedict & McMahon, 2006; United States Environmental Protection Agency, 2014) such as groundwater recharge (Winston, Dorsey, & Hunt, 2016) stormwater filtration and retention (Kubal, Haase, Meyer, & Scheuer, 2009; Liu et al., 2014; Page, Winston, Mayes, Perrin, & Hunt, 2015) and harbouring biodiversity’ (Vähä-Piikkiö, Kurtto, & Hahkala, 2004) the results also suggests that the same category provides an array of ‘Social and Cultural’ services (such as mental health and active enjoyment) as well as provisioning services (places to move for pedestrians).

Given that the sample of relevant academic literature within the review was relatively small (29 papers), some gaps in the demonstrated functions were expected. However, using the physical components of infrastructure to help categorize various elements into groups provides a replicable method of classifying infrastructure elements, and avoids the ambiguity inherent in Davies’ et al. (2006) original method using the green-grey continuum. The benefits of using a clearer method of defining green, grey and green-grey infrastructure within streets allows the various stakeholders and professionals to avoid definition ambiguity when working in an inter-disciplinary environment. Clear definitions are important for successful implementation of projects, as definition ambiguity has been shown to cause issues with path dependency and unclear expectations (Matthews et al., 2015; Wright, 2011).

5.1.2 Functions The multitude of landscape services provided by various street elements demonstrated in the literature corresponds with the general trend of streets becoming increasingly complex and multifunctional. As seen in Table 4.1 (page 24), infrastructure elements within all three categories (green, green-grey and grey infrastructure) had demonstrated their ability to provide landscape services in all three major categories. The most variety of services provided was in the ‘Social and Cultural’ category. This could be explained by the fact that urban settlements are designed for human needs, therefore most elements within a street can be expected to provide at least some services which fit into the ‘Social and Cultural’ category. The high level of academic interest in the ‘Social and Cultural ‘ landscape services of green infrastructure also points at an anthropocentric focus within the literature. This could be due to a perceived need to justify the placement of trees and planting into an often spatially constrained urban setting (Tjallingii, 2003), as well as the background of the researchers examining the green infrastructure elements, with many of them being from social sciences or transportation engineering backgrounds. The recurring theme of

37 hydrological functions provided by green-grey infrastructure elements is in line with the way ‘Green Infrastructure’ is often defined in North American contexts, with many researchers referring to their hydrological functions above all others (Mell, 2012). While green and green-grey infrastructure provided a wide array of landscape services in the ‘Social and Cultural’ and ‘Regulating and Maintenance’ categories, grey infrastructure was demonstrated to consistently provide ‘Provisioning’ services with a focus on the improvement of pedestrian space. This could be a reflection of an academic interest in the enhancement of pedestrian environments within streets.

5.2 W H A T I S K N O W N A B O U T T H E B O D Y O F L I T E R A T U R E ?

5.2.1 Geographic distribution and infrastructure types The majority of the studies are published in new-world countries. This correlates with the large number of studies located in suburban settings (69%). This dominance of new-world and suburban settings may indicate a promising sign that researchers are attempting to address the issues brought on by post-was suburban development patterns by looking at ways to improve residential streets. The large portion of papers published in the U.S. is also likely due to the States generally having a higher research output than many other countries (King, 2004).

The constant presence of rain throughout the year in the most commonly studied climate types corresponds with much of the green-grey stormwater infrastructure case studies within the body of literature. The strong focus on green-grey stormwater control measures in North America appears to be in line with Mell’s (2012), finding that in much of the U. S. ‘Green Infrastructure’ is most commonly seen as a stormwater management approach (Mell, 2012). While the high number of publications with this focus may contribute to a skewed perspective of green-grey infrastructure being associated with ‘blue’ functions above others, it is also reflective of the primary climatic issues being addressed.

5.2.2 Research questions and professional affiliations The most commonly asked research question within the academic literature was with regards to resident use and perception, followed by questions regarding the efficiency of green-grey stormwater systems. The significant percentage of papers investigating the use and perception of the streets by local residents are published primarily in the US and the UK. This testing of accepted design theories could signify a growing interest in the experiences of the end user, contrasting with the top-down approaches of post-war suburban street planning practices in the 1940’s and 1950’s (Southworth & Ben-Joseph, 2003).

A strong interest in the efficiency of stormwater systems can be linked to the sizeable presence of the environmental engineering profession, and may indicate that there is still an actual or perceived need for researchers to prove the effectiveness of green-grey stormwater treatment systems. This can be related to an attitude of mistrust toward green-grey stormwater solutions described by Olorunkiya et al. (2012). The large number of papers using experimental data collection methods corresponds to the large percentage of natural sciences-affiliated authors. In addition, the technical complexity of these case studies often requires more authors to collaborate on a research project than case studies carried out by social sciences researchers; this likely contributes to the large

38 representation of these professions. Higher diversity in disciplines found in papers researching perceptions and use of street elements could be an indicator of more collaboration in the academic fields looking more broadly at a street as a system than those who study individual elements. The overall high diversity in disciplines found within the body of academic literature on green, grey and green-grey infrastructure in streets corresponds to the multitude of professions governing various elements within a street described by Karndacharuk et al. (2014) in their review of urban shared street concepts.

5.2.3 Relevance to Practice

The professional affiliations of the researchers within this literature review are much more varied than the landscape architecture-dominated researchers usually contributing to the publications studied by Milburn and Brown (2016) (e.g. 77% of articles in the Landscape Journal are published by Landscape Architects). Despite the disciplinary scope being much more varied in this research and most of the papers being case studies, the most studied topic within the review was indeed perception and use by residents. Interestingly, the second most studied topic was the effectiveness of stormwater management function of specific infrastructure elements, which is more in line with the issues Milburn and Brown found to concern practitioners. This also applies to several studies investigating the biodiversity contributions of various infrastructure elements. While the disciplinary scope of this systematic review expands far beyond landscape architecture, it is possible that practitioners may find much of the research within this review of some relevance to practice. Milburn and Brown (2016) also alluded to the high value both researchers and practitioners put on the collation of existing academic information in order to make it more accessible. While not all academics believed this task to be specifically ‘research’ (Milburn & Brown, 2016), it can be argued that systematic reviews produce such an account by synthesizing existing academic knowledge in order to answer questions relevant both to research and practice.

5.2.4 Use of case studies when designing street retrofits The development patterns of countries, along with geographic and climatic contexts of the studies, appear to dictate the primary issues that infrastructure elements address, and the functions they are designed to perform. When the design of street retrofits takes place, relying too heavily on case studies that may be climatically different to the site in question can potentially result in ineffective and inappropriate elements being designed into a street. It would be pertinent for designers, planners and other professions involved in planning street retrofits to thoroughly research the local climatic conditions, soil properties, cultural norms and surrounding urban form before deciding which case studies may be appropriate sources of inspiration for a street renovation project.

5.3 I N T E G R A T I O N

Traffic-calming schemes made up most of the integration cases in the reviewed body of literature. These most commonly consisted of numerous interventions such as the use of planters, paving patterns and tree planting being implemented together in a deliberate manner to calm vehicular traffic and improve the pedestrian environment. This type of integration is widespread throughout research rooted in urban design and social sciences, and has a tendency to view green and grey-

39 green elements primarily as traffic-calming devices, often overlooking other landscape services. In contrast to the street-scale integration literature, the narrower focus of the element-scale integration achieves a more multi-functional use of a single element within a street. Considering that space in urban environments is often limited (Tjallingii, 2003), especially so within a street easement (Page, Winston, Mayes, et al., 2015b; Page, Winston, Mayes, Perrin, & Hunt Iii, 2014), this approach has considerable merit. Whilst the benefits are not always directly of an anthropocentric nature (such as a permeable-pavement car park infiltrating stormwater), their multiple uses make them valuable elements within the limited street space. A cross-over of the two integration approaches happens in two cases, found in the Coulson et al. (2011) and Page et al. (2014) papers. In these articles, both street-scale and element-scale integration takes place. Although the primary focus of the two authors differs significantly; Page et al. (2014) looks at the engineering efficacy of drainage systems whist Coulson et al. (2011) focuses on the social effects of a full-street retrofit, the utilization of both integration approaches could be an effective way to address spatial constraints while achieving an overall well-functioning street environment. The increasing pressure to accommodate multiple services and functions within the limited street space is efficiently addressed by element- scale integration, where multiple elements are combined within the same space in order to achieve multifunctionality. At the same time, the whole street is designed as a holistic system that serves a multitude of landscape services that were not previously available in a typical post-war suburban street.

In the context of the historic evolution of streets, it makes sense that integration at various scales is taking place in the literature. As streets have evolved through the centuries to be more complex spaces (Girling & Helphand, 1994; Southworth & Ben-Joseph, 2003), more and more elements have been introduced into the street corridor to meet the needs of its users at the time. In the last century, as technology evolved and the academic and professional fields involved in street design have began to understand the importance of design and ecosystem health to human well- being, street-wide traffic calming schemes have become a sensible and an important tool which harnesses the power of integration to improve the street environment. At the same time, as the understanding of the multiple benefits presented by vegetated elements within the street has increased, new green and green-grey infrastructure elements have been developed, and more of these elements are being implemented into, and studied in, new and retrofitted streets.

5.4 B A R R I E R S A N D E N A B L E R S

5.4.1 How could the barriers to implementation be overcome? The results of the narrative literature review suggest that the most common barriers to the implementation of infrastructure within a residential street easement were high costs, lack of space and negative perceptions of/lack of use by local residents. High costs presenting a barrier were in line with the findings of Forsyth (2005), just as the issue of spatial constraints was previously described by Bain et al. (2012).A lack of collaboration or communication between various disciplines, however, was not found to be a barrier within the academic literature. These differ from the most common barriers described at the planning scale; definition ambiguity and path dependence were not explicitly addressed by any of the authors within the systematic literature review.

Costs Higher costs of innovative infrastructure retrofits, in comparison with traditional grey infrastructure, formed a considerable barrier to implementation. The consensus in the broader literature about the cost-effectiveness of green-grey infrastructure in place of grey infrastructure is often mixed, with some studies claiming significantly higher installation costs (Page, Winston, Mayes, et al., 2015b; Page et al., 2014) and other researchers arguing relative cost-effectiveness, with high costs being only a perceived barrier (Olorunkiya et al., 2012). While this still remains contested, it appears that in many cases long-term lifecycle and cost assessment often provide a better economic value over time when compared to traditional business-as-usual infrastructure renewal (de Larrard et al., 2013).

Public asset retrofits do not generally provide an economic return such as investment in private development (Tjallingii, 2003). With the focus in the literature shifting from an eco-centric one to a more integrated view of green-grey infrastructure, an argument can be made for capitalizing on all the multiple functions of integrated street retrofits, as a focus on social and monetary benefits often outweighs arguments for only ecological benefits when political decisions are made. An economic assessment of all the other benefits of green-grey infrastructure (such as described by Vandermeulen, Verspecht, Vermeire, Van Huylenbroeck, and Gellynck (2011)) could potentially be used as a tool to compare against business-as-usual solutions. Along with this, the increased well- being of residents of well-retrofitted streets would decrease government health expenditure (Annear et al., 2009).

Space Lack of space within a street easement was found to be a considerable physical constraint to what infrastructure elements can be retrofitted into it. Despite this, a number of studies have found that some infrastructure such as rain gardens (Schlea, Martin, Ward, Brown, & Suter, 2014) and bioretention basins (Chapman & Horner, 2010) can, in fact, function well within the limited space of a street. Targeting the historically wide carriageways of suburban residential streets for retrofits provides an opportunity to allocate more space to innovative infrastructure solutions. The use of element-scale integration could also be an avenue to introduce more infrastructure elements and landscape services into the limited space of a street, without negatively affecting its usability by the local residents.

Perception Church (2014) suggests that negative perception of local residents can potentially affect the successful implementation of government schemes in retrofitting streets. Olorunkiya et al. (2012) suggest that much of the uncertainty in relation to green-grey infrastructure has been due to a lack of understanding and knowledge of its effectiveness. Therefore, explaining the efficiencies and operation of many new green-grey infrastructure elements may help to educate the public about which functions infrastructure elements are supposed to provide, and which they are not.

There is some consensus within the wider literature that public perception of a neighbourhood street is strongly linked to aesthetic value of the street (Coulson et al., 2011; Joan I. Nassauer, 1995), which has impact on a range of factors from a sense of well-being and safety (de Vries, van Dillen, Groenewegen, & Spreeuwenberg, 2013; Evers, Boles, Johnson-Shelton, Schlossberg, & Richey, 2014), and to affecting a sense of custodianship (Church, 2014; Hunter, 2011) and adjacent property value (Bourassa, Hoesli, & Sun, 2005). In the cases of street-scale integration within the literature, many papers explore the new (post-retrofit) aesthetics of a street as a contributing factor to their social success and frequency of pedestrian use (Adams & Cavill, 2015; Charlton et al., 2010; Church, 2014; Coulson et al., 2011; Curl, Ward Thompson, & Aspinall, 2015; Shu et al., 2014). The creation of high- quality aesthetics could be an effective way to gain public support through ensuring the whole street environment is improved, as residents very often see their immediate surroundings as a ‘self portrait’ of who they are as individuals (Joan I. Nassauer, 1995). This, coupled with an informative approach that explains the various infrastructure elements to local residents, could further strengthen positive resident perceptions (Adams & Cavill, 2015; Church, 2014) and contribute to an overall pride of place and increase the likelihood of similar developments being implemented elsewhere.

Collaborative design The importance of an integrated design process in order to achieve high-quality street environments has been highlighted by many authors (Appleyard, Gerson & Lintell, 1981; Gehl, 1971; Jacobs, 1961; Robinson, 1971 in Karndacharuk, Winston and Dunn, 2014). The values that apply to an integrated design process at the broader scale, such as inter-disciplinary design and clear goals, could contribute considerably to overcoming the barriers found in the literature. Alongside a multi-disciplinary professional team, the use of participatory design approaches by actively involving the street residents in the design process could be a valuable approach in cultivating positive perceptions and high utilization post-implementation. The inclusion of communities in the planning process has the ability to encourage open dialogue, sharing of critical information and mutual agreement on proposed solutions, which can contribute to a decreased risk of conflicts of interest and a sense of ownership for the community (Billger, Thuvander, & Wa stberg, 2016).

5.4.2 Considerations for the design of suburban street retrofits Many authors agree that the design of green, grey, green-grey and integrated streets and elements is very site-specific. Biddulph (2012) suggests that it is crucial to understand the surrounding land use prior designing walkable street environments, in order to ensure the street design is appropriate for the amount of foot traffic. For example, a street design for a residential area adjacent to a commercial hub may be different to that of a quiet neighbourhood street. A number of studies within the review state the importance of understanding how outside factors can influence various infrastructure elements. For example, when designing biofiltration cells/swales or permeable

42 pavement, one must be aware of water table conditions, soil drainage and soil types (Chapman & Horner, 2010; Page et al., 2014), as well as the possibility of pollutant exfiltration (Bäckström, Viklander, & Malmqvist, 2006; Hatt, Fletcher, & Deletic, 2009) and clogging (Page, Winston, Mayes, et al., 2015). Each element must be tailored to address relevant issues, as every setting is unique.

C O N C L U S I O N

A clear system for the definition of green, grey and green-grey infrastructure developed within this research could improve and add clarity to inter-disciplinary communications. The findings suggest that defining green, grey and green-grey infrastructure at the street scale by the physical components which make up the infrastructure elements was effective. While all three types of infrastructure proved to be multi-functional, green-grey infrastructure had the widest breadth of various functions. The literature showed a wide variation in disciplinary scope and geographic origins, signifying a strong multi-disciplinary trend as well as the prominence of specific types of infrastructure in certain climatic conditions. This research also highlighted the complex and multi- disciplinary nature of residential street retrofits. When it comes to effective green, grey or green- grey infrastructure retrofit design, there is no single universal template. While there is a wealth of examples of successfully implemented street retrofits, designs must always be tailored explicitly to their climatic, geological, land use and cultural surroundings.

While a number of barriers to the successful implementation and design of innovative infrastructure in suburban streets have been identified, these can contribute to a greater understanding of how the barriers could be managed. The issue of potentially high costs of retrofitting streets with green, grey and green-grey infrastructure could be balanced by lower government health expenditure and the pay-offs of long-term cost effectiveness. Spatial constrains frequently encountered in the literature could be addressed by thoughtful integration of various elements, along with targeting already wide post-war suburban street settings for retrofitting. Negative resident perceptions and lack of utilization could be overcome by aesthetically designed street retrofits, education of residents and collaborative design approaches. As the aged post-war suburbs of new-world countries become increasingly deteriorated, retrofitting the streets with innovative and integrated green, grey and green-grey infrastructure could be one of the best ways to ensure they become healthy, safe and desirable places to live in the future.

Limitations of the research Although this review attempted to include all the relevant years possible, it was limited up to the year 2015, meaning that it will only remain relevant for a number of years before needing to be updated. The available data was a relatively small sample.

Opportunities for further research While the research examining street-wide infrastructure integration tends to have a strong anthropocentric focus, the number of implemented projects explored by such studies suggests that there is some merit to this approach. This urban-design focused, street-wide approach could play a

43 vital role in getting retrofit projects implemented, and further study of these projects could present an avenue for implementing more integration of green and grey infrastructure within street retrofits. Further research into how integration could be achieved would be valuable in order to understand how designers can make better use of the limited carriageway space whilst accommodating the maximum number of landscape services. Investigation into how the process of a street retrofit takes place would be also be useful, as well as research that would determine what must be considered for each infrastructure element present in a best-practice retrofitted street. Finally, it would be interesting to apply the green, grey and green-grey definition framework at a broad range of spatial scales to test and refine its effectiveness.

R E F E R E N C E S

Adams, E. J., & Cavill, N. (2015). Engaging communities in changing the environment to promote transport-related walking: Evaluation of route use in the ‘Fitter for Walking’ project. Journal of Transport & Health, 2(4), 580-594. doi:10.1016/j.jth.2015.09.002 Ahern, J. (2007). Green infrastructure for cities: The spatial dimension. In V. Novotny & P. Brown (Eds.), Cities of the Future: Towards Integrated Sustainable Water and Landscape Management. London, UK: JWA Publishing. Ahiablame, L. M., Engel, B. A., & Chaubey, I. (2013). Effectiveness of low impact development practices in two urbanized watersheds: retrofitting with rain barrel/cistern and porous pavement. J Environ Manage, 119, 151-161. doi:10.1016/j.jenvman.2013.01.019 Annear, M. J. (2008). "They’re not including us!” Neighbourhood deprivation and older adults’ leisure time physical activity participation. Lincoln University, Lincoln University. Annear, M. J., Cushman, G., & Gidlow, B. (2009). Leisure time physical activity differences among older adults from diverse socioeconomic neighborhoods. Health Place, 15(2), 482-490. doi:10.1016/j.healthplace.2008.09.005 ASCE, NAHB, & ULI. (1974). Residential streets: Objectives, principles and design considerations. New York and Washington, US: American Society of Civil Engineers National Assciation of Home Builders Urban Land Institute. Bäckström, M., Viklander, M., & Malmqvist, P. A. (2006). Transport of stormwater pollutants through a roadside grassed swale. Urban Water Journal, 3(2), 55-67. doi:10.1080/15730620600855985 Badland, H., & Schofield, G. (2005). Transport, urban design, and physical activity: an evidence-based update. Transportation Research Part D: Transport and Environment, 10(3), 177-196. doi:10.1016/j.trd.2004.12.001 Bain, L., Gray, B., & Rodgers, D. (2012). Living streets: Strategies for crafting public space. Hoboken, US: Wiley. Barnett, J. (1982). An introductin to Urban Design. New York: Harper & Row. Bastian, O., Grunewald, K., Syrbe, R.-U., Waltz, U., & Wende, W. (2014). Landscape services- the concept and its practical relevance. Landscape Ecology, 29. doi:10.1007/s10980- 014-0064-5 Benedict, M. A., & McMahon, E. T. (2006). Green infrastructure: linking landscapes and communities. Washington, DC: Island Press. Biddulph, M. (2012). Street Design and Street Use: Comparing Traffic Calmed andHome ZoneStreets. Journal of Urban Design, 17(2), 213-232. doi:10.1080/13574809.2012.666206 Billger, M., Thuvander, L., & Wa stberg, B. S. (2016). In search of visualization challenges: The development and implementation of visualization tools for supporting dialogue in urban planning processes. Environment and Planning B: Planning and Design. doi:10.1177/0265813516657341 Boarnet, M. G., Forsyth, A., Day, K., & Oakes, J. M. (2011). The Street Level Built Environment and Physical Activity and Walking: Results of a Predictive Validity Study for the Irvine Minnesota Inventory. Environment and Behavior, 43(6), 735-775. doi:10.1177/0013916510379760

Bourassa, S. M., Hoesli, M., & Sun, J. (2005). The price of aesthetic externalities. Journal of Real Estate Literature, 12(2), 167-187. Brander, L. M., & Koetse, M. J. (2011). The value of urban open space: meta-analyses of contingent valuation and hedonic pricing results. J Environ Manage, 92(10), 2763- 2773. doi:10.1016/j.jenvman.2011.06.019 Brown, R. A., & Borst, M. (2014). Evaluation of Surface and Subsurface Processes in Permeable Pavement Infiltration Trenches. Hydrological engineering. Cambridge Dictionary. (2015). Cambridge Dictionary Online. Retrieved 08 June, 2015,from http://dictionary.cambridge.org/dictionary/english/street. Carle, M. V., Halpin, P. N., & Stow, C. A. (2005). Patterns of watershed urbanization and impacts on water quality. Journal of the American Water Resources Association (JAWRA), 41(3). Chapman, C., & Horner, R. R. (2010). Performance Assessment of a Street-Drainage Bioretention System. Water Environment Research, 82(2). Charlton, S. G., Mackie, H. W., Baas, P. H., Hay, K., Menezes, M., & Dixon, C. (2010). Using endemic road features to create self-explaining roads and reduce vehicle speeds. Accident Analysis & Prevention, 42(6), 1989-1998. doi:10.1016/j.aap.2010.06.006 Church, S. P. (2014). Exploring Green Streets and rain gardens as instances of small scale nature and environmental learning tools. Landscape and Urban Planning, 134(2015), 229-240. doi:10.1016/j.landurbplan.2014.10.021 Cochrane Collaboration. (2011, March 2011). Cochrane Handbook for Systematic Reviews of Interventions. Retrieved 26/01/2016, 2016,from http://handbook.cochrane.org/. Collins, J. A., & Fauser, B. C. J. M. (2005). Balancing the strengths of systematic and narrative reviews. Hum Reprod Update, 11(2), 103-104. doi:10.1093/humupd/dmh058 Colvile, R. N., Kaur, S., Britter, R., Robins, A., Bell, M. C., Shallcross, D., & Belcher, S. E. (2004). Sustainable development of urban transport systems and human exposure to air pollution. Science of The Total Environment, 334-335, 481-487. doi:10.1016/j.scitotenv.2004.04.052 Cooke, T. J. (2013). Residential Mobility of the Poor and the Growth of Poverty in Inner-Ring Suburbs. Urban Geography, 31(2), 179-193. doi:10.2747/0272-3638.31.2.179 Coombes, P. J., Argue, J. R., & Kuczera, G. (1999). . Urban Water, 1, 335-343. Costello, S. B., Chapman, D. N., Rogers, C. D. F., & Metje, N. (2007). Underground asset location and condition assessment technologies. Tunnelling and Underground Space Technology, 22(5-6), 524-542. doi:10.1016/j.tust.2007.06.001 Coulson, J. C., Fox, K. R., Lawlor, D. A., & Trayers, T. (2011). Residents' diverse perspectives of the impact of neighbourhood renewal on quality of life and physical activity engagement: improvements but unresolved issues. Health Place, 17(1), 300-310. doi:10.1016/j.healthplace.2010.11.003 Coutts, A. M., White, E. C., Tapper, N. J., Beringer, J., & Livesley, S. J. (2015). Temperature and human thermal comfort effects of street trees across three contrasting street canyon environments. Theoretical and Applied Climatology, 124(1-2), 55-68. doi:10.1007/s00704-015-1409-y Curl, A., Ward Thompson, C., & Aspinall, P. (2015). The effectiveness of ‘shared space’ residential street interventions on self-reported activity levels and quality of life for older people. Landscape and Urban Planning, 139, 117-125. doi:10.1016/j.landurbplan.2015.02.019 Davies et al., C. (2006). Green infrastructure planning guide project: Final report. Annfield Plain: NECF. 46

De Groot, R. S., Wilson, M. A., & Boumans, R. M. J. (2002). A typology for the classification, description and valuation of ecosystem functions, goods and services. (41), 393-408. de Larrard, F., Sedran, T., & Balay, J.-M. (2013). Removable urban pavements: an innovative, sustainable technology. International Journal of Pavement Engineering, 14(1), 1-11. doi:10.1080/10298436.2011.634912 de Nazelle, A., Nieuwenhuijsen, M. J., Anto, J. M., Brauer, M., Briggs, D., Braun-Fahrlander, C., . . . Lebret, E. (2011). Improving health through policies that promote active travel: a review of evidence to support integrated health impact assessment. Environ Int, 37(4), 766-777. doi:10.1016/j.envint.2011.02.003 de Vries, S., van Dillen, S. M., Groenewegen, P. P., & Spreeuwenberg, P. (2013). Streetscape greenery and health: stress, social cohesion and physical activity as mediators. Soc Sci Med, 94, 26-33. doi:10.1016/j.socscimed.2013.06.030 Després, C., Brais, N., & Avellan, S. (2004). Collaborative planning for retrofitting suburbs: transdisciplinarity and intersubjectivity in action. Futures, 36(4), 471-486. doi:10.1016/j.futures.2003.10.004 Dobson, J., & Sipe, N. (2008). Unsettling suburbia- The new landscape of oil and mortgage vulnerability in australian cities. Griffith University: Griffith University. Dover, V., & Messengale, J. (2013). Street design: The secret to great cities and towns. Somerset, US: Wiley. Dumbaugh, E. (2005). Safe Streets, Livable Streets. Journal of the American Planning Association, 71(3), 283-300. Dumbaugh, E., & Li, W. (2010). Designing for the Safety of Pedestrians, Cyclists, and Motorists in Urban Environments. Journal of the American Planning Association, 77(1), 69-88. doi:10.1080/01944363.2011.536101 Dumbaugh, E., & Rae, R. (2009). Safe Urban Form: Revisiting the Relationship Between Community Design and Traffic Safety. Journal of the American Planning Association, 75(3), 309-329. doi:10.1080/01944360902950349 Dunham-Jones, E., & Williamson, J. (2009). Retrofitting suburbia: Urban design solutions for redesigning suburbs. Canada: Wiley. Evers, C., Boles, S., Johnson-Shelton, D., Schlossberg, M., & Richey, D. (2014). Parent Safety Perceptions of Child Walking Routes. J Transp Health, 1(2), 108-115. doi:10.1016/j.jth.2014.03.003 Forsyth, A. (2005). Reforming suburbia: The planned communities of Irvine, Columbia and the Woodlands. Berkley, US: University of California Press. Forsyth, A. (2012). Defining Suburbs. Journal of Planning Literature, 27(3), 270-281. doi:10.1177/0885412212448101 Forsyth, A. (2013). Global suburbia and the transition century: Physical suburbs in the long term. URBAN DESIGN International, 19(4), 259-273. doi:10.1057/udi.2013.23 Garceau, T., Atkinson-Palombo, C., Garrick, N., Outlaw, J., McCahill, C., & Ahangari, H. (2013). Evaluating selected costs of automobile-oriented transportation systems from a sustainability perspective. Research in Transportation Business & Management, 7, 43-53. doi:10.1016/j.rtbm.2013.02.002 Gårder, P. E. (2004). The impact of speed and other variables on pedestrian safety in Maine. Accident Analysis & Prevention, 36(4), 533-542. doi:10.1016/s0001-4575(03)00059-9 Girling, C. L., & Helphand, K. I. (1994). Yard - street - park: The design of suburban open space. New York, NY: Wiley. Girling, C. L., & Helphand, K. I. (1997). Retrofitting suburbia. Open space in Bellevue, Washington, USA. Landscape and Urban Planning, 36, 301-313.

Gómez-Baggethun, E., & Barton, D. N. (2013). Classifying and valuing ecosystem services for urban planning. Ecological Economics, 86, 235-245. doi:10.1016/j.ecolecon.2012.08.019 Gough, D., Oliver, S., & Thomas, J. (2012). An introduction to Systematic reviews. London, Great Britain: SAGE. Gough, D., Oliver, S., & Thomas, J. (2013). Learning from research: Systematic reviews for informing policy decisions. London: Institute of Education University of London. Guo, Z., Rivasplata, C., Lee, R., Keyon, D., & Schloeter, L. (2012). Amenity or Necessity? Street Standards as Parking Policy: Mineta Transportation Institute. Hao, T., Rogers, C. D. F., Metje, N., Chapman, D. N., Muggleton, J. M., Foo, K. Y., . . . Saul, A. J. (2012). Condition assessment of the buried utility service infrastructure. Tunnelling and Underground Space Technology, 28, 331-344. doi:10.1016/j.tust.2011.10.011 Harvey, C., Aultman-Hall, L., Hurley, S. E., & Troy, A. (2015). Effects of skeletal streetscape design on perceived safety. Landscape and Urban Planning, 142, 18-28. doi:10.1016/j.landurbplan.2015.05.007 Hatt, B. E., Fletcher, T. D., & Deletic, A. (2009). Hydrologic and pollutant removal performance of stormwater biofiltration systems at the field scale. Journal of Hydrology, 365(3-4), 310-321. doi:10.1016/j.jhydrol.2008.12.001 Hofman, J., Stokkaer, I., Snauwaert, L., & Samson, R. (2013). Spatial distribution assessment of particulate matter in an urban street canyon using biomagnetic leaf monitoring of tree crown deposited particles. Environ Pollut, 183, 123-132. doi:10.1016/j.envpol.2012.09.015 Horner, M. W. (2008). Spatial dimensions of urban commuting- a review of major issues and their implications for future geographic research. The Professional Geographer, 56(2), 160-173. doi:10.1111/j.0033-0124.2004.05602002.x Hunter, M. R. (2011). Impact of ecological disturbance on awareness of urban nature and sense of environmental stewardship in residential neighborhoods. Landscape and Urban Planning, 101(2), 131-138. doi:10.1016/j.landurbplan.2011.02.005 Ikin, K., Knight, E., Lindenmayer, D. B., Fischer, J., & Manning, A. D. (2013). The influence of native versus exotic streetscape vegetation on the spatial distribution of birds in suburbs and reserves. Diversity and Distributions, 19(3), 294-306. doi:10.1111/j.1472- 4642.2012.00937.x Jacobs, J. (1961). The death and life of great American cities. New York: Random House. Jennings, D. B., & Jarnagin, S. T. (2002). Changes in anthropogenic impervious surfaces, precipitation and daily streamflow discharge- a historical perspective in a mid- atlantic subwatershed. Landscape Ecology, 17, 471-489. Kambites, C., & Owen, S. (2006). Renewed Prospects for Green Infrastructure Planning in the UK. Planning, practice and research, 21(4), 483 - 496. doi:10.1080/02697450601173413 Karndacharuk, A., Wilson, D. J., & Dunn, R. (2014). A Review of the Evolution of Shared (Street) Space Concepts in Urban Environments. Transport Reviews, 34(2), 190-220. doi:10.1080/01441647.2014.893038 Kazemi, F., Beecham, S., & Gibbs, J. (2011). Streetscape biodiversity and the role of bioretention swales in an Australian urban environment. Landscape and Urban Planning, 101(2), 139-148. doi:10.1016/j.landurbplan.2011.02.006 Kim, D.-W., Deo, R. C., Chung, J.-H., & Lee, J.-S. (2015). Projection of heat wave mortality related to climate change in Korea. Natural Hazards, 80(1), 623-637. doi:10.1007/s11069-015-1987-0 King, D. A. (2004). The Scientific Impact of Nations. Nature, 430, 311-316. 48

Kiss, M., Takács, Á., Pogácsás, R., & Gulyás, Á. (2015). The role of ecosystem services in climate and air quality in urban areas: Evaluating carbon sequestration and air pollution removal by street and park trees in Szeged (Hungary). Moravian Geographical Reports, 23(3). doi:10.1515/mgr-2015-0016 Knight, S. (2003). Integrating Stormwater Management with Economic, Social, Cultural and Ecological Goals in Christchurch, New Zealand. Australasian Journal of Environmental Management, 10(3), 181-191. doi:10.1080/14486563.2003.10648589 Kong, F., Yin, H., & Nakagoshi, N. (2007). Using GIS and landscape metrics in the hedonic price modeling of the amenity value of urban green space: A case study in Jinan City, China. Landscape and Urban Planning, 79(3-4), 240-252. doi:10.1016/j.landurbplan.2006.02.013 Krier, R. (2003). Town spaces: Contemporary interpretations in traditional urbanism. Boston, MA: Birkhauser - Publishers for Architecture. Kubal, C., Haase, D., Meyer, V., & Scheuer, S. (2009). Integrated urban flood risk assessment – adapting a multicriteria approach to a city. Natural Hazards and Earth System Sciences, 9(2009), 1881-1895. Leaf, W. A., Preusser, D. F., & United, S. (1999). Literature review on vehicle travel speeds and pedestrian injuries. [Washington, D.C.] : Springfield, Va.: U.S. Department of Transportation, National Highway Traffic Safety Administration ; National Technical Information Service [Distributor]. Retrieved from http://catalog.hathitrust.org/Record/003491998 http://hdl.handle.net/2027/mdp.39015048868973 Lee, S., & Green leigh, N. (2005). The Role of Inner Ring Suburbs in Metropolitan Smart Growth Strategies. Journal of Planning Literature, 19(3), 330-346. doi:10.1177/0885412204271878 Liu, W., Chen, W., & Peng, C. (2014). Assessing the effectiveness of green infrastructures on urban flooding reduction: A community scale study. Ecological Modelling, 291, 6-14. doi:10.1016/j.ecolmodel.2014.07.012 Lynch, K. (1960). The image of the city. Cambridge, MA: Technology Press. Mackie, H. W., Charlton, S. G., Baas, P. H., & Villasenor, P. C. (2013). Road user behaviour changes following a self-explaining roads intervention. Accid Anal Prev, 50, 742-750. doi:10.1016/j.aap.2012.06.026 Matthews, T., Lo, A. Y., & Byrne, J. A. (2015). Reconceptualizing green infrastructure for climate change adaptation: Barriers to adoption and drivers for uptake by spatial planners. Landscape and Urban Planning. doi:10.1016/j.landurbplan.2015.02.010 May, M., Tranter, P. J., & Warn, J. R. (2008). Towards a holistic framework for road safety in Australia. Journal of Transport Geography, 16(6), 395-405. doi:10.1016/j.jtrangeo.2008.04.004 MEA. (2007). Millennium Ecosystem Assessment. Meineke, E. K., Dunn, R. R., Sexton, J. O., & Frank, S. D. (2013). Urban Warming Drives Insect Pest Abundance on Street Trees. PLOS one, 8(3). doi:10.1371/ Mell, I. C. (2012). Can you tell a green field from a cold steel rail? Examining the “green” of Green Infrastructure development. Local Environment, 18(2), 152-166. doi:10.1080/13549839.2012.719019 Milburn, L.-A. S., & Brown, R. D. (2016). Research productivity and utilization in landscape architecture. Landscape and Urban Planning, 147, 71-77. doi:10.1016/j.landurbplan.2015.11.005

Moos, M., & Mendez, P. (2014). Suburban ways of living and the geography of income: How homeownership, single-family dwellings and automobile use define the metropolitan social space. Urban Studies, 52(10), 1864-1882. doi:10.1177/0042098014538679 Mueller, N., Rojas-Rueda, D., Cole-Hunter, T., de Nazelle, A., Dons, E., Gerike, R., . . . Nieuwenhuijsen, M. (2015). Health impact assessment of active transportation: A systematic review. Prev Med, 76, 103-114. doi:10.1016/j.ypmed.2015.04.010 Nassauer, J. I. (1995). Messy Ecosystems, Orderly Frames. Landscape Journal, 14(2). Nassauer, J. I. (2011). Care and stewardship: From home to planet. Landscape and Urban Planning, 100, 321-323. doi:10.1016/j.landurbplan.2011.02.022 Nassauer, J. I., Wang, Z., & Dayrell, E. (2009). What will the neighbors think? Cultural norms and ecological design. Landscape and Urban Planning, 92(2009), 282-292. doi:10.1016/j.landurbplan.2009.05.010 National Association of City Transportation Officials. (2013). Urban street design guide (978- 1-61091-534-2 (Online)): Island Press. Nickel, D., Schoenfelder, W., Medearis, D., Dolowitz, D. P., Keeley, M., & Shuster, W. (2013). German experience in managing stormwater with green infrastructure. Journal of Environmental Planning and Management, 57(3), 403-423. doi:10.1080/09640568.2012.748652 Nicoll, B. C., & Armstrong, A. (1998). Development Ofprunusroot Systems in a City Street: Pavement Damage and Root Architecture. Arboricultural Journal, 22(3), 259-270. doi:10.1080/03071375.1998.9747209 Novotny, V. (2013). Water–energy nexus: retrofitting urban areas to achieve zero pollution. Building Research & Information, 41(5), 589-604. doi:10.1080/09613218.2013.804764 Nowak, D. J., & Crane, D. E. (2002). Carbon storage and sequestration by urban trees in the USA. Environmental Pollution, 116(2002), 381-389. Olorunkiya, J., Fassman, E., & Wilkinson, S. (2012). Risk: A Fundamental Barrier to the Implementation of Low Impact Design Infrastructure for Urban Stormwater Control. Journal of Sustainable Development, 5(9). doi:10.5539/jsd.v5n9p27 Page, J. L., Winston, R. J., & Hunt Iii, W. F. (2015). Soils beneath suspended pavements: An opportunity for stormwater control and treatment. Ecological Engineering, 82, 40-48. doi:10.1016/j.ecoleng.2015.04.060 Page, J. L., Winston, R. J., Mayes, D. B., Perrin, C., & Hunt, W. F. (2015). Retrofitting with innovative stormwater control measures: Hydrologic mitigation of impervious cover in the municipal right-of-way. Journal of Hydrology, 527, 923-932. doi:10.1016/j.jhydrol.2015.04.046 Page, J. L., Winston, R. J., Mayes, D. B., Perrin, C. A., & Hunt Iii, W. F. (2014). Retrofitting Residential Streets with Stormwater Control Measures over Sandy Soils for Water Quality Improvement at the Catchment Scale. Environmental Engineering, 141(4). doi:10.1061/(ASCE)EE Petticrew, M., & Roberts, H. (2006). Systematic reviews in the social sciences: a practical guide. Malden, MA, USA: Blackwell Publishing. Qin, H.-p., Li, Z.-x., & Fu, G. (2013). The effects of low impact development on urban flooding under different rainfall characteristics. Journal of Environmental Management, 129, 577-585. doi:10.1016/j.jenvman.2013.08.026 Ridley, D. (2012). The literature review: a step-by-step guide for students (2nd edition ed.). London, Great Britain: SAGE.

/5%.CFC6)'5/.C FCU.#$4CFOZXYYPF)6$4674$4$8)$9/&2$#$564).&6,)6;4)5+5 &7."6)/./&"4)-2"652$$#F!&,&$0+!+=*.&,!'&4BAOYPCZ]L[[F #/)EYXFYXY^K*F2FZXYXFX\FXX[ .#5641-CF FOZXXZPF 4$$. .&45647"674$,..).').4!.9$#$.F$&&!& *,! &+* 4?EO\PC[_[L[`]F#/)EYXFYX`XKXZ^a_\]XZY^[]^ .#5641-CF FC.'$,56-CFCU (+$$CFOZXX^PF4!."/-24$($.5)8$2,..).'M )#$.6)&;).'!44)$45&/46($-).6$.."$/&&7."6)/.,(!)66.$69/4+5F &+( &*&$&&!& 4ECOYLZPC\[L]_F#/)EYXFYXY^K*F,.#74!2,.FZXX\FYYFXY^ .5,/.$C FC 7.'CFC).'C FCU.)$4)CFOZXYZPF),646)/..#",/'').'/&2$4-$!,$ 28$-$.6,/#$#!;74!.#4).'$F,*+4BDOZXPC^_^[L^__\F #/)EYXFYXY^K*F964$5FZXYYFYXFXY` "(,$CFC46).C FFC4#CFFC4/9.CFFCU76$4CFFOZXY\PF$4&/4-."$.# 6$4!,$$52/.5$5/&$64/&)6). 4#$.5F 0*'$' !$& !&*!& 4?GO`PF #/)EYXFYX^YKOP $,!$4'C FOYaa^PF/#.#64&&)"$.8)4/.-$.6F &+(&*&$&&!& 4ACCY][L Y_ZF $22$,6CFC/4-..CFFC22).+CFFC76$.!"(CFCU"(-)#6CFOZXYYPF37.6)66)8$ 4$8)$9/&$"/5;56$-5$48)"$567#)$5E224/"($5C5(/46"/-).'5.#6($4/#($#F '-*&$'(($!'$' 04BFO[PC^[XL^[^F#/)EYXFYYYYK*FY[^]LZ^^\FZXYXFXYa]ZF: (7CFC7)4/5CFFC.'CFCU(7CFOZXY\PF(.'$5/&564$$675$.#/.L4/#)4 37,)6;!$&/4$.#&6$4"/-2,$6$564$$64$64/&)6E.$:2,/46/4;"5$567#;)..6 /.)"C,)&/4.)F*&+('*,,!'&+* *,5*&+('*,&&.!*'&%&,4A@C [`_L[a^F#/)EYXFYXY^K*F64#FZXY\FX`FXZ\ /76(9/46(CFCU$.L /5$2(CFOZXX[PF,*,+&, (!& ''/&+&!,!+OZXX[ $#FPF5().'6/.CE 5,.#4$55F 264)CFC7CFCU/.6,6/CFFOZXYYPF)&$";",$)-2,)"6)/.5/&74!.'4$$. ).&45647"674$F&.!*'&%&,$'$$-,!'&4?CGO`LaPCZY_\LZY_aF #/)EYXFYXY^K*F$.82/,FZXYYFXYFXY] 24$)4$'$.CFFOYa^]PF*&+! &5 * !,,-*','/&+&!,!+F$9/4+ 8$.#5$.CFC/46(4)#'$CFFCU$6",&CFFOZXYZPF .6$'46).''4$;.#'4$$. ).&45647"674$6/)-24/8$6($($,6(.#9$,,L!$).'/&74!.2/27,6)/.5F!,!+& &.!*'&%&,4COYPF FOZXYXPF '&'%!+''+0+,%*.!+5!&+,*%!& , '&'%!+'&,-*5 '$' !$&'&'%!'-&,!'&+F/.#/.L5().'6/.E46(5".F$64)$8$# &4/-(662EKK999F6$$!9$!F/4'K4$5/74"$5K$"/5;56$-L5$48)"$5K $4-/45(7)<$.C FFCU2#-CFOZXXaPF.#5"2$5$48)"$55!4)#'$!$69$$. ,.#5"2$$"/,/';.#5756).!,$#$8$,/2-$.6F &+('$' 04@BO`PCYX[_L YX]ZF#/)EYXFYXX_K5YXa`XLXX`La[Y\L` *,,).'))CFFOZXX[PF 4$$..#4$#L$.$-)$5/4,,)$5B($64$"($:2$4)$."$9)6('4$$. 5647"674$2,..).'F-!$,&.!*'&%&,4GOZPCYX_LYY^F

A P P E N D I X A

How the keywords were used

Words from groups 1,2 and 3 were combined into search strings. e.g.: ((“footpath” OR “pave*” OR “sidewalk”) AND (“street” or “road” or “right-of-way” or “carriageway”) AND (“retrofit” or “repair” or “resurface” or “renewal” or “upgrade”)).

Words in Group 1 were changed in each search string until the search process was complete. Words in groups 2 and 3 were present in every search string.

A P P E N D I X B

Authors (year) Journal Location of study Retrofit USA

Brown and Borst (2014) Journal of Hydrological Engineering Louisville, Kentucky yes

Chapman and Horner (2010) Water Environment Research Washington yes

Church (2014) Landscape and Urban Planning Portland, Oregon yes

Evers (2014) Journal of Transport & Health Eugene, Oregon no

Harvey, Aultman-Hall, Hurley, and Landscape and Urban Planning New York no Troy (2015) Hunter (2011) Landscape and Urban Planning Ann Arbor, Michigan no

Meineke, Dunn, Sexton, and Frank PLOS One Raleigh, North Carolina no (2013) Page, Winston, and Hunt Iii (2015a) Ecological Engineering Wilmington, North Carolina yes

Page, Winston, Mayes, Perrin, and Journal of Hydrology Wilmington, North Carolina yes Hunt (2015b) Page, Winston, Mayes, Perrin, and Journal of Environmental Engineering Wilmington, North Carolina yes Hunt (2014) Schlea, Martin, Ward, Brown, and Journal of Hydrological engineering Westerville, Ohio yes Suter (2014) Shu, Quiros, Wang, and Zhu (2014) Transportation Research Part D Santa Monica, California yes

Adams and Cavill (2015) Journal of Transport & Health England yes

Biddulph (2012) Urban Design International England no

Coulson, Fox, Lawlor, and Trayers Health & Place England yes (2010) Curl, Ward Thompson, and Aspinall Landscape and Urban Planning England, Wales and Scotland yes (2015) Nicoll and Armstrong (1998) Arboricultural Journal England no

Sarkar, Webster, Pryor, Tang, Melbourne, Zhang, and Jianzheng Landscape and Urban Planning England no (2015) EU Backstrom, Viklander, and Malmqvist Urban Water Journal Sweden no (2007) International Journal of Pavement de Larrard , Sedran, and Balay (2011) France yes Engineering de Vries, van Dillen, Groenewegen, Social Science and Medicine Netherlands no and Spreeuwenberg (2013) Hofman, Stokkaer, Snauwaert, and Environmental Pollution Belgium no Samson (2013) Australia

Coombes, Argue, and Kuczera (1999) Urban Water Newcastle no

Hatt, Fletcher, and Deletic (2009) Journal of Hydrology McDowall, Queensland yes

(Ikin, Knight, Lindenmayer, Fischer, & A Journal of Conservation Biogeography Canberra no Manning, 2013) Kazemi et al (2011) Landscape and Urban Planning Melbourne no

Young, Daniels, and Johnston (2007) Australian Ecology Adelaide no

New Zealand Charlton, Mackie, Baas, Hay, Accident Analysis and Prevention Auckland yes Menezes, and Dixon (2010) (Mackie, Charlton, Baas, & Villasenor, Accident Analysis and Prevention Auckland yes 2013)

A P P E N D I X C