Assessment of Large-Scale Transitions in Public Transport Networks Using Open Timetable Data: Case of Helsinki Metro Extension

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Weckström, Christoffer; Kujala, Rainer; Mladenovic, Milos; Saramäki, Jari Assessment of large-scale transitions in public transport networks using open timetable data: case of Helsinki metro extension

Published in: Journal of Transport Geography

DOI: 10.1016/j.jtrangeo.2019.102470

Published: 01/07/2019

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Please cite the original version: Weckström, C., Kujala, R., Mladenovic, M., & Saramäki, J. (2019). Assessment of large-scale transitions in public transport networks using open timetable data: case of Helsinki metro extension. Journal of Transport Geography, 79, [102470]. https://doi.org/10.1016/j.jtrangeo.2019.102470

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Journal of Transport Geography

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Assessment of large-scale transitions in public transport networks using open timetable data: case of Helsinki metro extension T ⁎ Christoﬀer Weckströma, , Rainer Kujalab, Miloš N. Mladenovića, Jari Saramäkib a Department of Built Environment, Aalto University, Finland b Department of Computer Science, Aalto University, Finland

ARTICLE INFO ABSTRACT

Keywords: Transforming a direct radial network to a trunk-feeder system is an often-argued method of large-scale overhaul Accessibility in public transport networks. In planning such large-scale network overhauls, planners are often facing a di- Public transport network lemma when trying to achieve a careful balance between efficiency and equity, as overhaul might result in an Transit planning unequal distribution of benefits and burdens for end users. Despite theoretically well-known trade-offs between Transport justice trunk-branch and trunk-feeder networks, there are limited empirical studies documented from the user per- West metro spective, accounting for both travel time and transfers. Conventional methods used in practice, such as cost- benefit analyses, are often lacking the capacity to take into account equity effects. Having in mind the need for drawing lessons from actual overhauls, this research presents the assessment of changes in travel time and number of transfers brought about by the Helsinki metro extension, which involved the transformation of a direct bus network to a metro system with feeder buses. To this end, we develop a methodology for assessment of large-scale public transport network overhauls, building upon the previous development in service-equity assessment methods. Based on the use of open timetable data, the methodology centers on continuous journey calculations between all public transport access points. Thus, this methodology highlights the changes in travel time and transfers that would not be noticed in an aggregate assessment approach. In particular, the methodology reveals the disaggregate effects of the network overhaul from a three-level spatial perspective. As a result, this before-after study contributes to the understanding of the trade-offs between trunk-branch and trunk-feeder networks, while providing planning process recommendations for future large-scale public transport network overhauls.

1. Introduction this ongoing paradigm shift, as PTN overhauls are often made using public funding, their planning requires a careful balance between effi- Large-scale public transport network (PTN) overhaul often affect ciency and equity. As an example of efficiency concerns, PTN planning large geographic areas and significant population. Such major service has often been framed by the agency's perspective, focusing on such changes of PTNs can involve additions or replacements of transport aspects as cost (e.g., fleet size or operating cost) or resource utilization modes (e.g., upgrade to a higher right-of-way and higher capacity), (e.g., vehicle crowding, service coverage, and deadheading) (Thompson often related to land use changes (Nielsen et al., 2005; Walker, 2011). and Matoff, 2003; Vuchic, 2005). Following the general argument of Moreover, the significance of the overhaul can be determined based on distributive justice theory, in addition to aggregate effects, planning the percentage of routes affected, and include a combination of changes decisions should consider the distribution of effects (Martens, 2012; in the fare structure, spatial structure (e.g., route alignment, station Pereira et al., 2017,b;Linovski et al. 2018; Karner and Niemeier location), and temporal structure (e.g., changing headways, service 2013).When thinking about equity, the assumptions that planners use is hours). The recent worldwide trend in PTN overhaul is to suggest that passengers prefer fast, frequent, and direct PTN services without transformation of direct radial routes (trunk-branch network) to a transfers (Wardman 2004; Garcia-Martinez et al. 2018; Vuchic 2005; transfer-based system (trunk-feeder network), including timetable re- Gschwender et al. 2016). However, as agency's cost constraints require design (Vuchic, 2005; Hidalgo and Graftieaux, 2008; Sivakumaran that some origins and destinations are connected using transfers as et al., 2014; Salazar Ferro and Behrens, 2015; Mees, 2010). Following opposed to using direct routes, there are trade-offs between travel time

⁎ Corresponding author at: Department of Built Environment, Aalto University, Otakaari 4, 02150 Espoo, Finland. E-mail address: christoffer.weckstrom@aalto.fi (C. Weckström). https://doi.org/10.1016/j.jtrangeo.2019.102470 Received 20 June 2018; Received in revised form 26 June 2019; Accepted 1 July 2019 0966-6923/ © 2019 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY license (http://creativecommons.org/licenses/BY/4.0/). C. Weckström, et al. Journal of Transport Geography 79 (2019) 102470 and transfers in defining PTN alternatives. Within this context, planners the net benefits (Van Wee and Roeser 2013; Martens 2011; Beukers are often facing a dilemma when trying to balance efficiency and et al. 2012). Consequently, the wider distribution of effects for users equity, having at hand a difficult choice between multiple alternatives was not a component of this PTN overhaul assessment. Recognizing the that are often equally (un)desirable (Rittel and Webber 1973). Thus, planning dilemma of simultaneously accounting for aggregate and there is a need to inform further both theory and practice of PTN distributive effects, the aim of this research is to assess the distribution overhauls based on trunk-feeder principles. of impacts for users after an actual large-scale PTN transformation to a While the principles for planning and general trade-offs between trunk-feeder network. Following this analysis, the second aim is to trunk-branch and trunk-feeder networks are well known from a theo- provide lessons for planning future large-scale PTN transformations. retical standpoint (Gschwender et al. 2016; Jara-Díaz et al. 2012), there Having in mind the need to balance efficiency and equity aspects, the are very few real world cases where the changes are documented from a analysis considers both the user as well as the macroscopic perspective, user perspective. For example, minimum headways for individual PTN including the whole urban PTN. Drawing from gaps in the previous routes are often dictated by policy rather than demand. Thus, trunk- research in assessing changes from large-scale PTN overhaul, and ac- branch arrangement in some cases requires providing excess service on counting for the details of this particular case, this before-after study the branches to ensure the policy headway on the trunk section (Furth focuses on the following research questions: and Wilson 1981). Consequently, common trunk section may, de- pending on the overall demand pattern, have an even higher excess of 1. What are the aggregate changes in travel times and numbers of capacity, leading to low vehicle load factors and therefore resource transfers at different times of day? underutilization (Nielsen et al. 2005). Comparatively, a trunk-feeder 2. What are the disaggregate changes in travel times and numbers of network allows reducing this excess service on the trunk section and the transfers, accounting for specific trip origin and destination loca- number of separate vehicles and drivers, while still maintaining the tions, in relation to the metro expansion plan? policy-required headways on the feeder services. In addition, transition 3. What is the relation between aggregate and disaggregate effects of to trunk-feeder requires aiming for faster trunk section to mitigate some the PTN overhaul? of the burdens caused by the added transfers between the trunk and feeder routes. Similarly, transfers can be made more convenient by With these aims in mind, this paper consists of the following six implementing transfer synchronization or by increasing the service sections. The second section provides a background overview of studies frequency (Vuchic 2005). What is theoretically expected is that areas about large-scale PTN overhaul analysis and PTN assessment methods close to the trunk route stations will typically have the same or better for distributive effects. Section three describes PTN overhaul planning service than with direct bus routes, while negative aspects of a trunk- and implementation process in relation to the Helsinki metro extension, feeder system will concentrate on the PT users relying on feeder con- providing information about general changes in public transport service nections. provision after the overhaul. Section four presents the open-data Given the premise that transitioning to a trunk-feeder network methodological framework for PTN overhaul assessment, including might result in an unequal distribution of benefits and burdens for end assessment measures, data, as well as the algorithm and analytical users, there is a need for further developing the knowledgebase for formulations using travel time and number of transfers. Section five future PTN overhauls. Previously, there has been a stream of develop- shows the result of the multidimensional assessment of the West Metro ments in large-scale PTN planning and assessment methods. On the one effects, including aggregate and disaggregate effects at selected loca- side, a set of methods has mainly focused on using heuristic optimiza- tions. The following section six provides a discussion of results, with tion approaches capable of mathematical formulation for complex implications for large-scale PTN assessment methodologies and plan- large-scale PTNs (Guihaire and Hao 2008; Ibarra-Rojas et al. 2015; ning processes, including explicit normative aspects. Finally, section Bagloee and Ceder 2011; Cipriani et al. 2012). However, these methods seven concludes the paper with recommendations for further research are capable of only tackling parts of the network design problem and related to methodological development and case studies of large-scale often do not consider the distribution of benefits in the assessment. PTN overhauls. Moreover, although providing an extensive body of knowledge in PTN planning, the application of these methods to actual large-scale PTN 2. Background overhauls has remained limited. On the contrary, there has been a significant stream of development in PT service-equity assessment 2.1. Previous studies on large-scale PTN overhauls methods (Karner and Golub, 2015,b;Karner, 2018, b). While this stream of literature has focused on accessibility, often including aspects Previously, there has been a limited set of studies that measure ef- of land use, there has been a lack of case studies that would aim to fects on end-users caused by PTN overhauls. One of the first studies understand direct effects of the PTN restructuring (Silva et al. 2017; focused on several envisioned bus network overhauls and distribution Martens 2016). Moreover, previous development of PTN routing algo- of effects on different population groups in Belfast, using a supply rithms has focused dominantly on travel time. Thus, tradeoffs between measure combining PT frequency and coverage Wu and Hine (2003).A travel time and transfers that are at the center of planners' dilemma in follow up study was performed after the realized overhaul by Blair et al. planning trunk-feeder systems are not explicitly accounted for. These (2013). Here, spatial analysis of the changes in PT frequency was used gaps have also been enhanced due to difficulties in accessing data or the to find areas winning or loosing from the overhaul, revealing the stated extra effort required in modeling these large-scale changes (Karlaftis effects of the overhaul on citizens' daily life. El-Geneidy and Levinson and Tsamboulas 2012; Karner, 2018,b;Karner et al. 2016). (2007) measured the changes in number of jobs reached with car and Having in mind the need for drawing lessons from actual PNT PT between 1990 and 2000 in Minneapolis. This study focused on long overhauls, the recently completed first stage metro extension and sub- term changes in the PTN in a period with no large-scale redesigns. sequent PTN overhaul in the Helsinki Capital Region, Finland, provides Despite some implemented changes in the PTN, the measured impact of an excellent opportunity for a case study. PTN overhaul in the Helsinki these remained small. Another study on long-term (1996–2006) Capital Region has involved the transition from bus-based trunk-branch changes was performed on Toronto's PTN (Foth et al., 2013). Contrary operation to trunk-feeder operation based on metro and bus combina- to the Minneapolis study, the Toronto PTN had several PT investments tion. Similar to the dominant transport planning practice, cost-benefit completed during the period, including a new metro branch with five analysis was utilized for assessment of this metro extension in the new stations and seven new commuter train stations. The study linked planning stage. Here, the gains and losses were assessed from an ag- the changes in access to jobs using PT to the spatial distribution of gregate, i.e., utilitarian, perspective, where the focus is dominantly on wealth on a neighborhood level. Farber and Fu (2017) used an

2 C. Weckström, et al. Journal of Transport Geography 79 (2019) 102470 advanced continuous travel time measure with two case examples, Salt combinations of means of transportation and life situations. While most Lake City and Portland. The Salt Lake City case involved an expansion studies focus on spatial gaps, also the temporal dimension has been of the light rail and commuter train systems, while the bus services studied. For example, Farber et al. (2016) studies the temporal mis- were cut back. In the Portland case the effects of a 10% service re- match of PT demand and supply for population groups needing PT duction were measured. Here, the comparison was made over a shorter services in off-peak hours. In particular, the temporal dimension has period, between years 2011–2014 and 2009–2013 respectively. A fur- been studied when analyzing the accessibility to food stores (Widener ther study on Salt Lake City focused on the distributive effects of et al. 2015; Tenkanen et al. 2016). Apart from the distributive dimen- changing fare system from flat fare to a distance based fare (Farber sion, methodological differences also arise from the range of ways to et al. 2014). Anderson et al. (2013) studied Minneapolis focusing on the define and calculate the travel component. On the one hand, these timespan 2010–2030. Multiple combinations of land use and trans- measures range from the PT supply and coverage typically measured portation networks were studied, featuring multiple PTN alternatives. through frequency and walking distance boundaries at the simplest. On Another study focused on the extension of the Rio De Janeiro BRT- the other hand, these measures include continuous travel time measures system (Pereira 2019). A related body of PTN change literature studies taking into account the PT schedule structure and the diurnal variations the effects of high speed rail. Here, contrary to many studies focusing of travel time. In addition, advanced PT accessibility measures can take on city regions, these studies tend to be and focus on specific, defined into account other travel impedance factors such as monetary cost (El- changes in the PTN. The measures range from measuring travel time Geneidy et al. 2016), number of transfers (Kujala et al. 2018b), or a changes to one destination (Martínez Sánchez-Mateos and Givoni variety of travel time components (Kaplan et al. 2014). Furthermore, 2012), to the gravity-based weighted opportunities measure measuring also the measurement scale impacts the results, as most studies use jobs in distinct industries (Chandra and Vadali 2014). Furthermore, Cao census zones as a basis of analysis. Although involving development of et al. (2013) used a combination of several measures, such as weighted sophisticated models, accessibility gap studies have rarely been used to average travel time and cumulative opportunities index in studying the study PTN overhaul, or to provide lessons for trunk-feeder system impacts of the Chinese high speed rail project. To conclude, previous planning. large scale PTN overhaul studies have focused on the combination of land use and PT change. As a consequence, providing deeper implica- 3. Case study definition tions for planning based on changes in PTN structure has proven especially difficult for the particular case of urban trunk-feeder system. 3.1. PTN overhaul in Helsinki Metropolitan area

2.2. PTN distributive impact assessment methods Helsinki Metropolitan area is often considered as an area with highly-developed PTN, and with high ranking in user satisfaction (HSL, In the recent decades, there has been an increasing emphasis on 2018). Recently, there have been large investments in public transport developing assessment measures and methods from a user-centric per- network of the Helsinki Metropolitan area. One of these projects, the spective (Barabino and Di Francesco 2016; Curtis and Scheurer 2017). first stage of the West Metro project, finished in 2017, expanded the These previous measures have ranged from travel time, waiting time, current east-bound metro line to the southwestern parts of the Helsinki in-vehicle travel time, to number of transfers and passenger cost. The Metropolitan area. At the cost of 1186 million Euros, metro network has development of distributive impact assessment methods has largely been extended by 14 km, including eight new stations, five out of which been under the paradigm shift towards accessibility planning (Curtis include Park and Ride. The second stage of West Metro is currently and Scheurer 2010). Thus, earlier studies have a strong anchoring in under construction, and projected to finish in 2024. While the project both the land use dimension of accessibility research and the demo- was named after the central rail infrastructure, the project also involved graphic dimension of social justice research. In particular, the limita- substantial changes in the bus network, i.e., transforming a trunk- tions in reaching destinations using PTN caused by location of residence branch network to a trunk-feeder network. This was the case also with or belonging to a disadvantaged group of population (i.e., accessibility the initial east-bound metro section, opened in 1982, as the feeder- gaps) have been a focus of several studies. One accessibility gap trunk system was retrofitted in the existing suburban fabric. The West methodology focuses on comparing spatial match of the supply to the Metro has seen a very long planning process with alignment, technical need for public transport in Melbourne (Currie 2010). A similar supply solutions and arguments for the project changing trough the decades measure was used to study the accessibility gaps of elderly, low-income even before the inauguration of the initial east-bound metro section. and, no-car population groups in Perth (Ricciardi et al. 2015). A more Before construction, the West Metro was evaluated at several oc- sophisticated approach used a cumulative opportunities measure, casions, following for the most part standard practices in cost-benefit quantifying the number of services reachable within a fixed travel time analysis. These analyses were based on travel forecasts and estimated budget. Kaplan et al. (2014) utilized this method combined with an construction costs, as well as comparison of the existing or improved advanced routing tool when studying spatial, vertical, and inter- trunk-branch bus network to the suggested metro option based on a generational equity in Copenhagen. A similar approach was used when trunk-feeder network. During this planning process, one of the main studying vulnerable social groups in Montreal (El-Geneidy et al. 2016). arguments for the metro option was a potential for increasing the land Potential accessibility can also be measured without fixed travel time use density within the metro corridor (Espoon kaupunki, 2005; thresholds using the weighted travel time measure, where travel times Länsimetro Oy, 2008; YTV 1987). Another argument for the metro are weighted with the available opportunities (Fayyaz et al. 2017). option was a threat of increasing congestion of the road network for the A further variation of the potential accessibility measure is to apply reliability and speed of surface modes, such as buses. Travel time es- a distance decay function to weight the destinations, in order to better timates were included in the forecasting model, and detailed examples reflect the actual travel patterns (Fransen et al. 2015). Karner (2018, b) of travel times between specific origin-destination pairs were provided used a set of gravity based accessibility measures to study the equity of as supplementary information. However, the travel time estimates were the PTN in Phoenix. The accessibility measures were further used to calculated using a static network representation and therefore only evaluate individual routes in the PTN. Modeling actual behavior even provided coarse estimates of the travel times. more closely is possible through statistical models linking personal traits to travel behavior. Using this approach, it is possible to measure 3.2. Overview of changes in the service provision the accessibility for groups of people sharing the same profile (Järv et al. 2018). This approach was used by Páez et al. (2012) when Changes in the service provision included both the route planning as studying the accessibility of day care facilities while assuming various well as schedule recalculation. As a summary, Table 1 shows the

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Table 1 calculated as separate, regardless of being a part of a station or terminal Summary of various network statistics, showing the situation before and after complex. Overall, vehicle kilometers for metro increased 66% while the the West metro. service provided by bus is decreased by 9%. Contrastingly, values for Number of stops Route kilometers Vehicle kilometers tram, commuter train and ferry are mostly unchanged. In addition to this table, the scale of the changes can be seen from Fig. 1 below. Panel Mode Before After Before After Before After on the left depicts PTN spatial layout and daily load (in vehicles per day) in the Helsinki Metropolitan area before the overhaul, while panel Tram 268 269 131 134 22,558 22,837 ﬁ Subway 17 25 65 107 17,438 28,874 on the right of this gure depicts PTN the situation after the overhaul. Rail 38 38 345 345 28,651 28,685 Observing the changes in space, one can conclude that many direct bus Bus 5662 5630 4954 4886 417,932 376,506 lines going to the city center have been completely removed and re- Ferry 4 4 12 12 242 242 placed with feeder bus routes, converging mainly at two of the eight Total 5989 5966 5507 5484 486,821 457,144 new metro stations. number of PT access points, route kilometers and vehicle kilometers for 4. Methodology each mode before and after the opening of the West Metro. The statistics are based on single direction and describe the network for one 4.1. Methodological framework weekday, thus providing an example for the PTN overhaul scale. In detail, each stop or platform included and referenced in the data set are In order to draw implications for planners' dilemma, special A B

C D

Fig. 1. The PTN of the study area before (panel A) and after (panel B) the opening of the West Metro and the feeder bus system weighted by frequency. The approximate capacity measured in the number of seats of the routes for the respective cases are show in panel C and panel D. Background map (c) OpenStreetMap contributors, (c) Carto.

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Scale of analysis

Data requirements (proporon) Input

Macro (all-to-all) Meso (Zonal) Micro (Point of interest)

Degree of aggregaon High Low Output

Fig. 2. Framework showing the principles of aggregation and the outputs for different scales of analysis. attention has been dedicated to usefulness for planning practice, often avoid (Silva et al. 2017; Boisjoly and El-Geneidy 2017). Moreover, through interaction with practicing PTN planners during methodolo- special attention has been dedicated to the use of open data as an input gical development. To assess the distribution of benefits and burdens for analysis procedure, as this has been recognized as one of the major from a user-centric perspective, it is necessary to use a methodology opportunities for PTN planning (Davidsson et al. 2016; Kujala et al. capable at producing disaggregate results on a macroscopic level. While 2018a). Following the principles of open science, the scripts used for various types of cumulative opportunity indexes are excellent measures producing the results are released online (https://github.com/jweckstr/ when characterizing an area, they do not perform well when assessing westmetro_scripts). Details of each assessment scale in the framework the potential benefits and burdens experienced by individuals in a are explained in the following subsections. trunk-feeder system. In particular, an increase in travel time or transfers between a single pair of origin and destination points may have severe 4.2. Data consequences for some individuals. On the contrary, the same individual might not gain from improved accessibility to other locations. Similarly to many recent studies (Fransen et al. 2015; Farber et al. To overcome the challenges of producing an overview of the changes, 2016; Fayyaz et al. 2017; Karner, 2018,b;Hadas 2013), our before- the methodological framework is built with three main components, on after analysis uses two public transport schedule datasets in the General three scalar levels (Fig. 2). In particular, the macro scale information is Transit Feed Specification (GTFS) format (for a description of the aggregated, the meso-scale is zone-based, and micro scale is focused on format, see https://developers.google.com/transit/gtfs/). These data potentially least aggregated groups. By such combination of different sources are openly provided by the Helsinki Region Transport (HSL) levels of aggregation it is possible to enrich the aggregate levels of (see https://www.hsl.fi/en/opendata). The first dataset represents the analysis with information from the disaggregate levels, thus con- schedule before the West Metro and the second the new schedule with tributing to the aim of user-centricity on a macroscopic level. For this the West Metro and feeder routes in operation. The dates of the sche- formulation, an essential methodological premise is that PTNs have dules used in this case study are for the Wednesday, 25.10.2017, and both a spatial and a temporal dimension (Holme and Saramäki 2012; Wednesday, 10.01.2018, respectively, as representative analysis dates Gallotti and Barthelemy 2014). The spatial dimension consists of the without major schedule changes. In addition, this schedule data is access points such as stops, stations and terminals and the routes con- complemented with street-network-based walking distances, calculated necting these. The temporal dimension consists of the schedule that between stops that are 2 km or less apart using OpenStreetMap (OSM) dictates when and at what time the public transport user can expect to data. As this before-after analysis relies on comparisons of stop-to-stop travel to her destination. In addition, when considering the change in travel measures between same locations, it was necessary to make sure travel time, there is not always a need to establish a minimum threshold that each dataset included the same stops. To this end, before and after for accessibility over the whole region. In fact, it is expected that the databases were supplemented with the stop locations missing. accessibility levels over the region vary for a range of reasons, not limited solely to mobility aspects. As the combination of spatial and temporal structure impacts service quality from a user standpoint, this 4.3. Computing origin-destination travel times and transfers assessment methodology should be capable of a detailed spatio-temporal analysis for the whole PTN (Fig. 2). Additional aspects of use- The travel travel times and transfer values were calculated using a fi fulness for planning practice have been accounted for by limiting the modi ed version of the Connection Scan Algorithm (CSA), im- data requirements, and keeping the application procedures simple and plemented in the Python programming language, included in the gtfspy transparent. As already identified in the literature before, this approach package (https://github.com/CxAalto/gtfspy)(Dibbelt et al. 2017; is contrary to more advanced modeling approaches (e.g., with added Kujala et al. 2018b). In this algorithm, every connection between ad- behavioral component), which would require further sources of data joining stops in the transit schedule and connecting walking connec- and more sophisticated application procedures that planning agencies tions generated based on the schedule are scanned through in reversed temporal order. The walking connections in this methodology have a

5 C. Weckström, et al. Journal of Transport Geography 79 (2019) 102470 maximum distance of 2 km and the walking speed is set to 70 m/min. These mean measures provide an overview of changes, but are not The algorithm collects a set of journey alternatives that are Pareto- capable of showing the effects on a stop-to-stop basis. The last set of optimal with regards to departure time, arrival time and number of performance measures are the most aggregated, representing the transfers. The Pareto-optimality of trips is based on the trade-off be- system level averages, giving an indication of the overall direction of tween travel time and transfers: a trip is accepted as Pareto-optimal if changes. These measures are called all to all mean travel time (ATT) and an improved solution for a criteria cannot be found without declining all to all mean number of transfer (ANT) and are calculated as: any other criteria. In addition, the number of transfers is not limited in n 1 the routing process. However, a minimum transfer time of 3 min is ATT = ∑ MTTi n applied, which prohibits journeys with transfers that are likely to fail in i=0 (5) real situations. As a side-effect, this also discourages transfers in the n fi 1 routing, which is a general users' tendency. A travel time pro le is ANT = ∑ MNTi n created using the calculated Pareto-optimal trips, continuously de- i=0 (6) scribing the total travel time (including waiting time before the trip) where n is the total number of valid stop entries. between the origin and the destination, while also considering the number of transfers needed to reach the destination. The travel time 4.5. Analysis zones and focus locations profile in this methodology is calculated for a one-hour departure-time interval. However, the actual routing is calculated for three consecutive To study how the travel time changes in different locations in re- hours allowing also longer journeys to complete. Based on the travel lation to the metro extension, the study area has been divided into five fi time pro le generated, it is possible to produce performance measures assessment zones (AZ) based on the location in relation to the metro fi as described by Kujala et al. (2018b). The travel time pro le was then expansion (Fig. 2). In this zoning arrangement, each public transport used to calculate a mean travel time between all stops in the study area stop is a member in one of the zones. In the case a station could belong and the mean number of transfers for the fastest path trips. In parti- to multiple zones, classification preference is assigned ordinally, in the cular, the mean travel time approach assumes an informed PT user that following order which accounts for the position of the stop with respect always chooses the fastest trip option, but leaves at a random time. In to the network overhaul. The first AZ consists of the areas close to the addition, calculating the number of transfers while in the same time new metro stations (new metro stations). The second zone consists considering the travel time creates more reasonable results than using of areas that have lost the direct bus connections to the city center and methods based on a static network (Kujala et al. 2018b). will rely on feeder buses to the new metro stations (feeder bus area). Here we included stops from which at least half of the fastest path trips 4.4. Assessment measures to the city center passes via the new metro extension after the metro has been introduced. This step was necessary due to a “soft” boundary Following the above-mentioned premises and research questions, between the area relying on feeder buses and the area to the north assessment measures include three parts with different levels of ag- where there are the options on using the commuter trains, with or gregation. The basic unit of analysis for travel time is the average without feeder buses or direct bus connections to the city center. The origin-destination travel time (TTi, j), describing the average time to third AZ consists of the areas around earlier metro stations (old metro reach the destination j from the origin i when travel takes place spon- stations), the fourth AZ of areas around commuter train stations taneously without planning, that is taking into account the pre-journey (commuter train stations). The fifth AZ includes all other stops waiting time. TTi, j can be calculated as: that do not fit in any of the other categories (other stops), and that were not considered directly in the PTN overhaul. The zones centered 1 tend TTi,j = ∫ τtdti,j () around metro or commuter train stations are defined by a 800 m ttend− start tstart (1) walking distance threshold, in accordance to a commonly used esti- where tend and tstart are the end and start time of the analysis period, mation of a typical walking distance to transit discussed by Guerra et al. and τi, j(t) the travel time from access point i to access point j as a (2012). In addition to the AZ, a set of six stop locations were selected to function of time. represent the most detailed level of analysis and thus to demonstrate For transfers we calculate the number of vehicle transfers on fastest the spatial sensitivity of the overhaul impacts. Three stops are located paths, NTi, j, which calculates the mean number of required transfers along the metro in the city center, a key transfer point and destination when using the fastest route. Please note, that the word transfer here for PT in Helsinki. The additional three reference stops are located in also includes the first access to a PT route, not only transfers between the area of the PTN overhaul. routes. Thus, every trip trajectory where PT is used there is at least one transfer, while walking only trips has zero transfers. 5. Results

t 1 end jt∗ () NTi,j = ∫ bdt 5.1. Aggregate changes ttend− start tstart (2)

∗ where bj (t) is the number of transfers on the next fastest-path journey The ATT and ANT for diﬀerent times of day before and after the departing at time t or later. Based on these, the mean travel time to all West Metro are shown in Table 2. The average travel time to reach all destinations (MTTi) and mean number of transfers to all destinations destinations is roughly one hour for all time periods within the study (MNTi) are calculated, corresponding to the average travel time and transfer, respectively, needed to reach all other stops. These measures Table 2 are calculated as: Global averages for the ATT and ANT measures.

n 1 Time ATT ANT MTTi = ∑ TTi,j n j=0 (3) Before After Change Before After Change

n – − 1 7 8 0:58:37 0:59:06 0:00:28 2.466 2.447 0.018 MNTi = ∑ NTi,j 12–13 1:00:56 1:01:17 0:00:21 2.408 2.395 −0.013 n j=0 (4) 16–17 0:58:10 0:58:38 0:00:27 2.449 2.438 −0.011 21–22 1:01:41 1:02:31 0:00:50 2.286 2.273 −0.012 where n is the number of stops with a valid path to the stop in question.

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Fig. 3. The analysis zones used in the study. Background map (c) OpenStreetMap contributors, (c) Carto.

Fig. 4. Changes in MTT (panel A) and MNT (panel B) to all destinations for each origin stop during morning peak hour. Background map (c) OpenStreetMap contributors, (c) Carto. area. Furthermore, 2.4–2.5 transfers are required when using the fastest 5.2. Changes by analysis zone route option. The indicators suggest a small increase of ATT at all times of day, especially in the late evening. However, there is a slight de- The distribution of TT changes gives more insight on the effects for crease in ANT, suggesting a reduction in the average number of trans- specific origin-destination combinations (Panel A in Fig. 5). The dis- fers required. In addition to these most aggregate measures, the spatial tribution of change shows both increased and decreased travel times for distribution of MTT and MTB change reflects the area where the PTN most categories. However, TT for new metro stations is predominantly overhaul took place 4. For this figure, MTT and MNT measures are improving, with up to 15 min shorter travel times and only a few des- calculated considering all the PT access points as potential and equally- tinations with increased TT. In comparison, the main exception are valued destinations, for departures between 7:00 and 8:00 AM, i.e., travel times between stops in the new metro stations AZ and feeder bus morning peak hour. Presented in the right panel of Fig. 3, the ag- area AZ, which has a even distribution between positive and negative gregated changes for MNT follow a similar pattern as MTT. When changes in TT. Moreover, TT for the feeder bus area AZ is mostly in- considering all destinations, the new metro stations areas have an creasing, even beyond 15 min, with very few destinations with im- average MNT decrease of up to 0.6, while the average MNT for the proved values. However, there is still a number of origin-destination feeder bus areas will increase up to 0.5. (See Fig. 4). pairs where the changes are small. For transfers (Panel B), the direction of change are similar when considering the corresponding origin and

7 C. Weckström, et al. Journal of Transport Geography 79 (2019) 102470

Fig. 5. The change in travel time (panel A) and number of transfers (panel B) between and within the AZ in the morning peak hour.

8 C. Weckström, et al. Journal of Transport Geography 79 (2019) 102470

Fig. 6. TTi, j and NTi, j to specific stop locations, during the morning peak hour. Background map (c) OpenStreetMap contributors, (c) Carto. destination zones. The changes tend to be within an increase and de- Lasipalatsi and Rautatientori. In particular, TT and NT increases for crease of one transfer, for trips directly affected by the overhaul. Kamppi and Lasipalatsi stops overall, with the only exception being However, the new metro stations AZ experience decreases of up to one stops in the Otaniemi area. However, only a few hundred meters east is transfers on some trips to the old metro stations AZ. As can be expected, the tipping point, where the increase in NT caused by the introduction TT of trips completely outside the West Metro corridor are mostly un- of the feeder bus system is neutralized be the previously required ad- changed, as can be seen in the cells describing TT changes within and ditional transfer. Thus, to Rautatientori stop and locations further east between old metro stations, commuter trains stations and other stops along the metro, NT is not increasing for the feeder bus area, while NT AZs in Fig. 5. is decreasing for stops in the new metro station AZ. Travel time changes follow a similar pattern, although less abrupt. In particular, Kamppi area has the highest increases in TT, with increases of over 20 min 5.3. Impacts for selected locations possible. At Rautatientori stop, the increases are limited to 10 min, with a larger area having a reduced travel time. In order to highlight changes at representative locations, Fig. 6 Soukka, Matinkylä and Otaniemi are locations within the West shows the changes in TT and NT. In the upper part of the figure, one can Metro corridor, that is the metro station vicinities and the feeder bus observe the sensitivity of changes for city center locations, i.e., Kamppi,

9 C. Weckström, et al. Journal of Transport Geography 79 (2019) 102470 area. Soukka and Matinkylä experience similar patterns for NT and TT (Kamppi), as well as the areas extending northward from this location change. However, the TT change is much higher in Soukka, the station (see Fig. 6). These results suggests that the metro is not fast enough to being deep in the feeder bus area AZ, compared to the Matinkylä stop overcome the lost time in the feeder system, longer alignment of trunk which is on the border between the feeder bus area AZ and the new section, and the increased number of stops. Furthermore, the results metro station AZ. On the contrary, the effects for Otaniemi are com- suggest that the changes brought about by the second phase of the West pletely different. There are almost no areas with increases in NT nor TT. Metro are most likely not improving the MTA of the future metro sta- The decreases in NT and TT correspond the metro stations, both old and tions beyond the trunk-branch system. The situation for peripheral new. Furthermore, the areas relying on transfer points west of areas relying solely on feeder buses will likely stay as is. Rautatientori also show improvement. 6.2. Implications for planning methods and processes 6. Discussion Contrasting the findings from this study with theoretical arguments 6.1. Distribution of PTN overhaul effects about effects of trunk-branch and trunk-feeder networks highlights several aspects that should be taken into account in the future PTN The study attempts to give an accurate and nuanced description of overhaul planning. At the center of this reflection, we have to recognize the potential effects for individual PT users. Using travel time and an irreducible planner's dilemma in finding the right balance between transfer-based measures makes the direct effects of the PTN overhaul aggregate and disaggregate effects. Contrary to the dominant utilitarian easier to grasp. Findings indicate that travel time and transfer benefits logic often used in spatial planning, which focuses on aggregate effects, are concentrated around the metro stations both new and old, while the this study highlights the importance of distributional effects from PTN areas relying on feeder buses are generally carrying the burdens of transformation to a trunk-feeder network. In this particular context, we increased travel time. This effect was reflected in both the aggregate have to recognize that Helsinki Region Transport System Plan includes measures, mean travel time to all destinations (MTT) and mean number of an explicit focus on accessibility in the region (HSL, 2015). This is an transfers to all destinations (MNT) and the disaggregate measures average excellent example of the transition in planning practice, changing the origin-destination travel time (TT) and number of vehicle transfers on fastest focus from average vehicular speeds to the capability of reaching a paths (NT). However, this specific case of the West Metro is strongly destination. In this case study context, information about accessibility is influenced by the fact that the metro did not increase the speed of the even more important having in mind an equal access to opportunities trunk section but merely aligned the trunk section differently. for everyone, which is a dominant value of the Finnish society Furthermore, the results show that the areas benefiting from the metro (Rantanen et al. 2015). However, the idea of absolute equality is often were fairly well connected also before the metro, while some of the challenged by the basic properties of transport systems and the un- most severe travel time increases are imposed on areas with the longest derlying center-periphery topography. Essentially, the explanation is initial travel times. This is further accentuated with the fact the PT users rather straightforward – it is often difficult to have equal travel time for in these areas are also often required to transfer more. Thus, based on all the citizens across the region to, for instance, Helsinki city center. the results, the changes in travel time and number of transfers from the Thus, the core of planner's dilemma is how to find the acceptable bal- West Metro project were unequally distributed from a spatial perspec- ance of the unequal effects from PTN overhaul, while coping with the tive. multitude of design dimensions of trunk route alignment and stop lo- The general trend was larger travel time savings in the vicinities of cations. In addition, it would be important to highlight the notion that metro stations close to the city center and locations further away from planner does not face a binary decision between trunk-branch and the former bus trunk section. Consequently, station locations between trunk-feeder network. On the contrary, just as in the case of West the city center and the northward bend of the new metro section gained Metro, where some direct bus routes have been reintroduced for areas travel time savings of up to 10–15 min in MTT, while stations furthest with largest travel time increase, network design decisions are on a to the west gained only 5 min MTT. The connections between metro continuum. In such a network design process, while cumulative cost- station vicinities are improved where the past system lacked direct benefit analysis may be a useful step for assessment, it is not sufficient connections. when considering the consequences for individuals or for accounting While the areas relying on feeder buses in general experienced in- for non-monetary effects. Besides accounting for cost-benefit ratio, the creased travel times, in some areas travel times remained unchanged or use of variable criteria weights within a multi-criteria framework would even decreased. The differences between the past and new route open up more opportunities for deliberation about the effects for dif- alignments is the main reason of these differing effects. The most im- ferent citizen groups. Furthermore, as an example of aspects difficult to portant factors are the relative closeness of the metro stations compared measure monetarily, we have to recognize that many transport experts to the motorway and the degree in the high speed and direct alignment would agree that investment in West Metro is justified as a strategic of the highway was utilized by the direct bus route. In particular, areas mechanism for shifting land use policy towards a more sustainable di- where a large proportion of the distance of the bus system in the past rection. was covered on streets see small positive and negative effects, while Emphasizing on the process of planning, dilemma situations require areas where the high speed and direct alignment of the highway was a planner to make a difficult choice between two or more alternatives, utilized see strong MTT increases up to 15 min. The former is the case in that are often equally (un)desirable. In this process of planning, a areas north of the metro alignment while the latter occurs in the west planner might need to accept a dialectic between two contrasting views and along the motorway. Furthermore, in some instances also the old on social justice – namely utilitarian and Rawlsian logic. Similarly, we bus system relied on transfers for connections towards the city center. have based our methodological approach following both. The central In these cases the change to the metro improved travel times. message of classical utilitarianism is that an act is morally right if it The areas outside the new metro corridor show only minor changes maximizes the difference between the total amount of benefits and total in mean travel time, with a small overall increase. This may be inter- amount of burdens for all people. Following this idea, we have to be preted as a “shadow” effect of the changes seen in the West Metro thoughtful about the aggregate effects and aggregate resources of our corridor, where the stops with increased travel time dominate. When transport systems. For example, we would certainly want that our PT considering particular origins and destinations where changes occur, system results in the lowest possible amount of total CO2 tons emitted. the positive effects are concentrated along the old metro section and Following the utilitarian approach in this case study means a focus on areas that are well connected to the metro in the eastern parts of the calculating average net change in travel time and number of transfers. city. The clear looser is the former terminus of the motorway bus system However, what the findings above tell us is that a utilitarian approach is

10 C. Weckström, et al. Journal of Transport Geography 79 (2019) 102470 useful as an overview of the impacts, but inevitably does not reveal planning processes for PT investments are often dominantly focused on much about the distribution of impacts. Thus, solely focusing on ag- the infrastructure and network planning, where the scheduling process gregate benefits would misinterpret the implications for users, as ben- starts only after the investment decisions has already been made. In efits and burdens brought about by a PTN overhaul may vary between turn, further development of planning processes would require a more users even in the same spatial location. Contrary to the classical utili- thorough planning and assessment of the PT network and schedule at tarianism, distributive theories of justice underline the fact that the an earlier stage. Nowadays, these analysis steps can certainly be made distribution of effects matters, as it is not always desirable to violate possible with the increased availability of suitable planning support significantly the right of the few for the sake of the many. In one of the systems and the increased computing capacity. However, such re- most influential theories of distributive justice, John Rawls recognized commendations for planning processes ultimately lead to the question that inequalities may exist, as long as the benefits from the inequalities of roles and responsibilities of stakeholders within those processes and are accessible to all, and these inequalities are distributed to benefit the their broad goals. Ultimately, we arrive to the question of whether least well-off (Rawls 1971). Following this line of logic, if one analyses large-scale PT investments and system overhauls should be planned in a PTN impacts spatially, adverse inequalities will inevitably be noticed, more human-centered order, taking the desired service level for users as but it matters how adverse they are for particular people affected. From a starting point rather than the map-based infrastructural outlines. the findings above, one can conclude that distribution of changes on a zonal level, both within and between zones, provides a more nuanced 7. Conclusion view on the impacts that different origin-destination pair categories experience. This contrast between aggregate and distributed effects is at In order to provide implications for balancing efficiency and equity the core of this difficult choice that PTN planner would have to face. in planning practice, the study presented here developed a metho- However, just as many other dilemmas that often do not have a dology for quantifying the effects of large scale PT overhauls from straightforward resolution, recognizing that they exist is a major step in trunk-branch to trunk-feeder network. This methodology is applicable advancing further reflection. for any set of longitudinal PT schedule data. The methodology brings Focusing at the assessment methods, there are other detailed aspects user-centric performance measures to a macroscopic scale, enabling a to take into account in the future PTN overhaul planning processes. As more nuanced assessment of PTN overhauls. The impacts of transfor- in this case study, effects for specific locations can help in under- mation from a trunk-branch network to a trunk-feeder network were standing aspects that have been neglected in the original impact as- analyzed using two main approaches. The first approach is following a sessments. Here, one has to recognize that the point of measurement utilitarian logic, assessing the average net change in travel time and will heavily frame the results. For example, measuring effects at the number of transfers. The second approach assumes a distributive justice former bus terminus of the trunk-branch network will favor the bus, standpoint, where changes in travel time and transfers are assessed in a indicating an increase in number of transfers for all areas relying on disaggregate and distributed manner. As seen from the findings, the feeder buses. On the contrary, measuring effects at locations further transition from a direct bus network to a feeder-trunk network has away along the metro route will favor the metro, indicating a decrease different implications for PT users if observed from an aggregate or in number of transfers in all areas within walking distance to the metro disaggregate standpoint. In particular, the number of transfers required stations. Certainly, neither of the measurement locations are wrong as for passengers relying on feeder buses might increase, while the service they represent the travel patterns of many people, and will be affected level closer to the stations might improve. Having a detailed look at the by network structure properties. Moreover, effects will differ due to the distribution of effects, the trunk-feeder system might both mitigate and asymmetry of effects due to the changes in schedule structure. The aggravate the inherent inequality caused by location within a city. trunk-branch system has a more asymmetric service structure with frequent service in the peak direction and in some cases different route 7.1. Limitations and future research directions variants running in the opposite direction. Conversely, the trunk-feeder system is providing a more even service in both directions. The pattern This research focused on potential mobility from a user-centric of travel time changes are thus not only sensitive to location but also to perspective. However, to enhance interpretability and as a consequence the direction of travel. However, the central point is that travel time of solely relying on open data sources, the model has omitted several changes cannot be reliably assessed trough a narrow selection of origin- important factors impacting the individual's ability to utilize PT. Thus, destination pairs as was made in the original impact assessments. Thus, further research could take into account other user traits or capabilities, in order to provide a broader understanding of the benefits and burdens such as household structure, social status or age (Páez et al. 2012), from large-scale PTN overhaul, assessment practice in the future has to perceived accessibility (Lättman et al. 2018), or walking capabilities. In include a combination of stations, such as terminus stations of the particular, further integration of walking and PT routing is necessary trunk-branch network, and stations further away from the new trunk for creating accurate results. However, for computational reasons section. walking distances needs to be cut short, increasing the possibility of The results of this research showed that the generated total travel erroneous results on trips where walking is competitive. On the con- times for the metro option in the planning phase were optimistic trary, methodological development can account for walking distances compared to the realized schedules. In fact, travel time estimates within large PT stations and terminals, as these are rarely included in computed based on static network based transport models may not be openly available walking network datasets. For simplicity, in this re- accurate enough to take into account the complexities of a schedule- search only the fastest paths are considered. Moreover, there is a need based PT system. In the worst case, the travel time estimates may be to include service reliability indicators or aspects of PT fare scheme (El- misleading and lead to inferior designs. Metaphorically speaking, just as Geneidy et al. 2016), eventually leading to generalized cost approach our lives do not happen in static map-based plans, our PT trips do not that could produce more robust results. However, when considering the happen only on map lines without schedules. Not accounting for the differing preferences of PT users in relation to differences in PT system, fact that PTNs are temporal networks have most likely influenced both a more advanced approach would be to compare the results of several the results from cost-benefit analysis and consequently the decision preference profiles. process itself. Basing the argument on travel time estimates that neglect In addition, this study contains some limitations regarding gen- nuances of time calculation mechanisms might also undermine the eralizability of findings. Due to the case approach, the results regarding existing trust in Finnish planning institutions, especially in the cases of the justice dimension of trunk-feeder networks are not generalizable. such large public investments. The challenges identified here directly Furthermore, the case of the West metro is fairly unusual with the new relate to the components of the planning process itself. For instance, trunk section not increasing travel speeds. Thus, for better

11 C. Weckström, et al. Journal of Transport Geography 79 (2019) 102470 generalizability, it would be necessary to study several real-life cases of Transp. Res. A 91, 302–316. transitions from trunk-branch to trunk-feeder networks, and further Espoon kaupunki, 2005. Liikenne- ja viestintäministeriö, and YTV. In: Metro−/ Raideyhteys Välillä Ruoholahti - Matinkylä Ympäristövaikutusten Arviointiselostus. assess PTN transitions. In addition to more active analysis of large-scale Technical Report, Helsingin kaupunki. PTN overhauls worldwide, made easier by the widespread of open data Farber, S., Fu, L., 2017. Dynamic public transit accessibility using travel time cubes: sources, it is also necessary to continue investigating the possibilities for comparing the effects of infrastructure (dis)investments over time. Comput. Environ. Urban. Syst. 62, 30–40. distributive justice assessment in the planning processes. There is Farber, S., Bartholomew, K., Li, X., Páez, A., Nurul Habib, K.M., 2014. Assessing social clearly room for research on planning frameworks better adapted at equity in distance based transit fares using a model of travel behavior. Transp. Res. A integrating individual level impact assessment within the overall 67, 291–303. – planning process, especially by enhancing public engagement as part of Farber, S., Ritter, B., Fu, L., 2016. Space time mismatch between transit service and observed travel patterns in the Wasatch front, Utah: a social equity perspective. assessment procedures. With this in mind, one research strand should Travel Behav. Soc. 4, 40–48. continue investigating the possibilities that public engagement has for Fayyaz, S.K., Liu, X.C., Porter, R.J., 2017. Dynamic transit accessibility and transit gap – development of usable and useful planning support systems (Stewart causality analysis. J. Transp. Geogr. 59, 27 39. Foth, N., Manaugh, K., El-Geneidy, A.M., 2013. 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