Status and Future Directions for Residential Street Infrastructure Retrofit Research
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Review Status and Future Directions for Residential Street Infrastructure Retrofit Research Ksenia I. Aleksandrova, Wendy J. McWilliam and Andreas Wesener * School of Landscape Architecture, Faculty of Environment, Society and Design, Lincoln University, P.O. Box 85084, Lincoln 7647, Christchurch, New Zealand; [email protected] (K.I.A.); [email protected] (W.J.M.) * Correspondence: [email protected] Received: 12 April 2019; Accepted: 30 April 2019; Published: 3 May 2019 Abstract: Residential streets, particularly in automobile-dependent suburban locations, have frequently been perceived as ecologically unsustainable, antisocial, unhealthy, and aesthetically dull from an urban design perspective. However, residential streets can be improved through infrastructure retrofits, particularly by combining green and grey infrastructures and integrating various functions and services. Using a systematic literature review and an adapted landscape services framework, the paper analyses the status of retrofit research and discusses existing composition and spatial integration of green, grey, and green-grey street infrastructure. Findings suggest changing infrastructure compositions in residential streets and a trend toward increased grey and green-grey infrastructure integration. However, functional connectivity is often lacking, and while barriers to implementation have been suggested, few have been tested. While retrofits are potentially able to increase the number and quality of landscape services that support human well-being, more—and possibly longitudinal—research is required to advance and analyze their implementation and provide evidence for their success. Keywords: green infrastructure; grey infrastructure; green-grey infrastructure; landscape services; residential streets; street retrofits; infrastructure retrofits; urban design 1. Introduction Streets within residential communities perform various infrastructure functions. They provide conduits for communication, electricity, stormwater, sewage systems (i.e., utilities), and for pedestrians, cyclists, and automobiles. Furthermore, residential streets can increase social inclusion [1] and social cohesion [2]. They contribute to neighbourhood vitality, diversity, and sense of place [3]. Green infrastructure, such as street trees, contributes to positive aesthetic experiences, physical, and mental health, and increased property values [4]. In addition to mitigating microclimate in support of user thermal comfort [5], green infrastructure helps cleanse the air [6], and sequester carbon mitigating climate change [7]. It also provides support for indigenous wildlife, e.g., [8], and stormwater management services beyond those of conventional pipes, curbs, and gutters [9]. Beginning in the early 20th century, many residents were able to adopt automobiles as their primary mode of transport [10]. This led to the development of large scale, low-density residential neighbourhoods on the outskirts of city centres, that were not within walking or cycling distance of public transit or supporting land uses, such as employment and commercial centres [11]. While there has been some variation in residential street widths through time and with context, since about the 1930s many suburban residential street and carriageway widths have become increasingly wide. For example, Ben-Joseph [12] argued that since 1930, in many American cities, streets have been designed to maximize the speed and safety of drivers, with rights of way ranging from about 15 to 18 m (Figure1). 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