Measuring relative non-motorized accessibility to retail activities

Accessibility planning is a crucial alternative to mobility planning for reaching sustainable outcomes. Although there is a vast literature on accessibility, less attention is paid to accessibility as a relative concept, i.e., its relationship with the socio-economic characteristic of the population. While accessibility is known to vary by location, it also changes as a consequence of differences in individual willingness to reach destinations by certain transport modes. Using the city of Zaragoza, Spain as a case study, this paper evaluates relative non-motorized accessibility (walking and cycling) to three types of retail activities: daily, weekly, and incidental. First, a clustering process is used to identify four population groups according to their socio-economic characteristics (the young employed; the young unemployed; seniors and adults). Second, distance-decay functions based on time-willingness to reach retail destinations by non-motorized modes are compared between the four clusters of population. Third, relative accessibility maps based on gravity-based models are elaborated, highlighting places that exhibit statistical differences between the population clusters. The results indicate that willingness to reach retail stores on foot by seniors (>65?years old) was significantly different from the rest of groups analyzed, providing additional insights on how relative accessibility measurements can anticipate potential social exclusion risks.     

Measuring and visualizing place-based space-time job accessibility

Place-based accessibility measures, such as the gravity-based model, are widely applied to study the spatial accessibility of workers to job opportunities in cities. However, gravity-based measures often suffer from three main limitations: (1) they are sensitive to the spatial configuration and scale of the units of analysis, which are not specifically designed for capturing job accessibility patterns and are often too coarse; (2) they omit the temporal dynamics of job opportunities and workers in the calculation, instead assuming that they remain stable over time; and (3) they do not lend themselves to dynamic geovisualization techniques. In this paper, a new methodological framework for measuring and visualizing place-based job accessibility in space and time is presented that overcomes these three limitations. First, discretization and dasymetric mapping approaches are used to disaggregate counts of jobs and workers over specific time intervals to a fine-scale grid. Second, Shen's (1998) gravity-based accessibility measure is modified to account for temporal fluctuations in the spatial distributions of the supply of jobs and the demand of workers and is used to estimate hourly job accessibility at each cell. Third, a four-dimensional volumetric rendering approach is employed to integrate the hourly job access estimates into a space-time cube environment, which enables the users to interactively visualize the space-time job accessibility patterns. The integrated framework is demonstrated in the context of a case study of the Tampa Bay region of Florida. The findings demonstrate the value of the proposed methodology in job accessibility analysis and the policy-making process.     

Measuring cycling accessibility in metropolitan areas

Different measures of cycling accessibility have been widely introduced in transportation planning. However, those measurements are mainly restricted by the availability of travel behavior data. In addition, there has been limited comprehensive research on the importance of cycling accessibility to destinations based on the travel time or distance. In this paper, a new index for measuring bikeability in metropolitan areas is introduced. A Cycling Accessibility Index (CAI) is developed for quantifying cycling accessibility within local areas in metropolitan Melbourne, Australia. CAI is defined according to gravity-based measures of accessibility. This index measures cycling accessibility levels in terms of diversity of different land uses, number of activities in statistical areas, and the travel impedance between origins and destinations. The Victorian Integrated Survey of Travel and Activity (VISTA) dataset was used to evaluate the index and investigate the association between the cycling accessibility levels and the number of bicycle trips in local areas. The index is assessed by investigating the association between levels of cycling accessibility and the number of bicycle trips in statistical areas. Key findings indicate that there is a significant positive association between bike trips and the CAI.     

Robust accessibility: Measuring accessibility based on travelers' heterogeneous strategies for managing travel time uncertainty

Uncertainties in travel times due to traffic congestion and delay are risks for drivers and public transit users. To avoid undesired consequences such as losing jobs or missing medical appointments, people can manage the risks of missing on-time arrivals to destinations using different strategies, including leaving earlier to create a safety margin and choosing routes that have more reliable rather than fastest travel times. This research develops a general analytical framework for measuring accessibility considering automobile or public transit travelers' heterogeneous strategies for dealing with travel time uncertainty. To represent different safety margin plans, we use effective travel time (expected time + safety margin), given specified on-time arrival probabilities. Heterogeneity in routing strategy is addressed using different Pareto-optimal routes with two main criteria: faster travel time vs. higher reliability. Based on various safety margin and routing strategy combinations, we examine how accessibility changes under varying safety margin plans and routing strategies. Also, we define and measure robust accessibility: geographic regions that are accessible regardless of the safety margin planning and routing strategy. Robust accessibility can provide a conservative and reasonable view of accessibility under travel time uncertainty. To demonstrate the applicability of the methods, we carry out an empirical study on measuring the impacts of new transit service on healthcare accessibility in a deprived neighborhood in Columbus, Ohio, USA.     

Measuring the long-distance accessibility of Italian cities

Long-distance accessibility is a crucial element for economic development and for territorial cohesion. To be revealing, however, a measure of accessibility must not only consider the distance or travel time of a single mode, but should include the fares, the frequency and the interchanges of all available modes.The paper aims to address whether and where there is an accessibility problem between Italian regions, through a comprehensive measure of accessibility covering the entire Italian territory. The measure used in the paper is potential accessibility, with an exponential decay impedance function. Different from similar studies, this one gives a more in-depth definition of impedance parameters due to the availability of a transport model that includes the entire Italian long-distance supply (roads, coaches, long-distance rail services, air services, and ferries). The opportunities at destination are proxied by population, and private and public sector employees.The main outputs are detailed maps of accessibility that are significantly more realistic than using simple infrastructure indicators or single-mode measures. In addition, some policy conclusions are drawn in terms of past and future investment policies.     

Measuring the quality of port hinterland accessibility: The Ligurian case

Traditionally, distance was considered the parameter that could better reflect the economic influence of a seaport on land. Containerisation and intermodality progressively eroded such a paradigm and currently distance became only one of the factors across the overall “equation”. In this respect, a fundamental role is played by the effectiveness of inland connections. The better the connection of a port to the various inland markets, the bigger the potential to enlarge its overall captive area. Furthermore, the higher the “frictions” (bottlenecks, delays, etc.) for reaching the hinterland, the lower the inland traffic flows.The major purpose of the paper is to measure container traffic diversion from Ligurian ports (Genoa, La Spezia and Savona) to the main Italian and European competitors.The application of a gravity model will reveal the current role of distance in drawing hinterland market share among the selected ports. Moreover, for evaluating the unexploited potentialities of Ligurian ports, we compared real traffic flows with the outcomes of a spatial interaction model, reassigning inland container flows to the different sampled ports. The calculation of the traffic delta through a gap analysis, allowed measuring the “frictions” thwarting the connectivity between the Ligurian ports and the sampled hinterland regions. Finally, the paper discusses the nature and the reasons for the above traffic diversion.     

Measuring accessibility to grocery stores using radiation model and survival analysis

Measuring spatial accessibility to grocery stores and identifying food deserts have been of interest to planners and policy makers. However, measuring and quantifying accessibility in a way that relates to actual travel behaviors and preferences are challenging. This study aims to promote an existing radiation model by incorporating different transportation modes and time use diaries to provide a more realistic estimation of accessibility. We proposed a survival analysis method, such as the Cox proportional hazard model, as a novel approach to develop a cost decay function based on time use diaries. A multinomial logit model was applied to estimate the portion of people walking, traveling by car, and traveling by bus. A case study of grocery stores in Travis County, Texas, is used to illustrate the approach. The results indicate that for walking accessibility to grocery stores, the majority of zip codes fall into the very low, low, and moderate accessibility classes. Moreover, in most western zip codes transit accessibility to grocery stores is found to be very low. However, the spatial accessibility for some of such zip codes has been enhanced because of the presence of cars.     

Measuring spatial proportionality between service availability,accessibility and mobility: Empirical evidence using spatial equity approach in Iran

Spatial proportionality plays an important role in recognizing inequities, the quality of actions to reduce them, and halting complicated and unclear cycle of inequities and even reversing their increasing trend. The aim of this study is to measure spatial equity based on spatial proportionalities (SESP), taking into account three-fold factors including service availability, accessibility and mobility. The SESP identifies proportionality between the quality of service distribution and allocating opportunities and the quality of getting access to locations and people's selections according to status quo. Thus, it examines the balance between supply and demand, optimization of distance and the number of choices people make out of total services and the role of move ability to use in compensating for shortages either in terms of service capacity or the level of human deprivation and reduction of effects of distance from services and etc. Gorgan as an old and intermediate city in northern Iran was selected as the case study. The results indicated that the study area does not enjoy suitable proportionality, revealing that the central and northern districts have much more enjoyment than the southern, eastern and western districts. Thus, there is disproportionality between supply and demand, high difference in provided choices and disproportionality between less enjoyed areas and their move ability to use services and inability to create walking travel pattern in Gorgan. Understanding of spatial proportionality can help the planners and policy makers to change their passive role into active in order to reduce inequities, adding to their knowledge on the underlying factors of inequity as well as the factors that hinder and reverse the cycle of inequity.     

Measuring railway network performance considering accessibility levels in cities worldwide

There is a growing acceptance of and interest in transit accessibility-based developments as a means to address urban challenges, such as automobile dependency, air pollution, urban sprawl, and congestion. Additionally, prompting car drivers to switch to public transit requires the construction of attractive and accessible public transit systems. Accordingly, it is necessary to measure railway network performance while considering accessibility, which indicates the potential opportunity of interaction. Thus, this study aims to develop a railway network performance index (RPI) to evaluate transit accessibility, with regard to differences in travel speed, and conduct a comparative analysis of 40 cities worldwide. The major findings are as follows. European cities have a high RPI, but cities in developing countries have relatively low RPI values, due to railway infrastructure shortages. Railway and station density have a positive relationship with RPI, but differences in RPI emerge between cities with the same infrastructure levels. This difference indicates the importance of efficient railway system connections between the distributions of populations and facilities. Overall, this study enhances understandings of transit accessibility and provides benchmark points that may be useful for decision-making processes, transportation investments, and land use policies.     

Measuring accessibility to health care services for older bus passengers: A finer spatial resolution

Health care accessibility is a vital indicator for evaluating areas where there are medical shortages. However, due to the lack of population data with a satisfactory spatial resolution, efforts to accurately measure health care accessibility among older individuals have been hampered to some extent. To address this issue, we attempt to measure accessibility to health care services for older bus passengers in Nanjing, China, using a finer spatial resolution. More specifically, based on one month's worth of bus smart card data, a framework for identifying the home stations (i.e., a passenger's preferred station near their residence) of older passengers is developed to measure the aggregate demand at the bus stop scale. On this basis, a measurement that integrates the Gaussian two-step floating catchment area (2SFCA) and the adjusted 2SFCA methods (referred to as the adjusted Gaussian 2SFCA method) is proposed to measure accessibility to health care services for older people. The results show that: (1) almost all home stations experience inflated demand, especially those located in the suburbs; (2) despite abundant health care resources, home stations in urban districts are rarely identified as high accessibility stations, due to high demand densities among the older population; and (3) more attention should be paid to two types of home stations – those with a medical institution and those with bed shortages, respectively. The first type is predominantly distributed in the periphery of the city, in the suburbs where the travel time required to access the nearest health care service by bus is longer. The second type is mostly located in the outskirts of urban districts and in the central area of one suburb. These findings could help policy makers to implement more appropriate measures to design and reallocate health care resources.     

Measuring access to urban centres in rural Northeast Brazil: A spatial accessibility poverty index

This study proposes two innovative methods to measure transport-related exclusion in rural areas caused by the lack of access to basic opportunities (e.g. healthcare, education, jobs, etc). The Spatial Accessibility Poverty (SAP) indices, that are developed, are tailored for rural areas of the Global South and particularly illustrated in a case study in Northeast Brazil, where spatial data is most scarce. Gravity-based models are proposed based on travel impedance methods derived from i) Friction surface datasets, and ii) Kernel density maps. The spatial information is then aggregated at a municipality level creating indices that conjugate factors of severity and extent of SAP. The findings show that factors like deprivation of housing facilities (electricity and sanitation) and low population density are associated with critical SAP levels. The results also point out to higher prevalence of SAP in inner areas than the coastal areas of Northeast Brazil. The sensitivity analysis shows how data-poor contexts present a particularly complex environment to develop robust SAP measures. The findings emphasise the importance of considering sensitivity analysis and complementary factor analysis when applying SAP indicators for planning transport and for action prioritisation purposes. Since access to services and opportunities has been claimed to be a key difference between those who have escaped chronic poverty those still trapped in it, SAP indicators tailored to areas where poverty is most spread are of primary importance to promote a new standard of transport development strongly committed to eradicating poverty.     

Dynamic accessibility: Incorporating day-to-day travel time reliability into accessibility measurement

Travel times and hence accessibility in urban areas are susceptible to traffic disruption caused by events such as congestion, roadworks and traffic accidents. Being highly valued by travellers, travel time reliability affects their participation in activities and thus, plays a decisive role in accessibility. The aim of the study was to develop an approach to integrate travel time reliability into the measurement of accessibility. To achieve this, we extended a commonly-used accessibility indicator to include day-to-day variability in travel times. In a case study of the accessibility to the newly-built Queen Elizabeth University Hospital (QEUH) in Glasgow, we used real-time travel times with high temporal resolution collected over a long period of time to demonstrate the applicability and the utility value of this approach compared to the standard accessibility measurement. Our results revealed that travel time reliability varied both temporally and spatially, and zones experienced relatively high levels of accessibility loss due to higher travel time variability. The proposed approach provides a more realistic representation of actual network performance, allows for assessing the effect of travel time reliability on accessibility throughout the day and will help transport planners to trace equity impacts on accessibility due to travel time unreliability.     

Measuring the accessibility and spatial equity of urban services under competition using the cumulative opportunities measure

As accessibility becomes an increasingly relevant concept in the analysis of sustainable transport and urban development, the accuracy of accessibility measures becomes increasingly vital. While more complex measures are gradually gaining popularity with increasing data and computational resources, policy makers and planners are still prone to opt for less complex methods that are easy to use and interpret. The cumulative opportunities measure is the most widely applied accessibility measure in planning practice, but it is also among the least accurate due to its lack of consideration of the impact of competition for those opportunities. This study seeks to highlight the impact of addressing competition for different urban services in the cumulative opportunities measure. A competition component is added to the measure, which is applied to a case study of three types of urban services in the Perth metropolitan area; jobs, primary/secondary education and shopping. The results show that considering competition changes the spatial patterns of accessibility and its equity. Since this approach reveals demand-supply imbalances, it can more accurately determine spatial inequalities in accessibility, and hence increases the utility of the cumulative opportunities measure. We also find that the three services had varying levels and spatial patterns of accessibility and spatial equity, thus relying on any single one of them for assessing spatial structural performance can be misleading.     

Immigrant settlement patterns,transit accessibility,and transit use

Public transit is immensely important among recent immigrants for enabling daily travel and activity participation. The objectives of this study are to examine whether immigrants settle in areas of high or low transit accessibility and how this affects transit mode share. This is analyzed via a novel comparison of two gateway cities: Sydney, Australia and Toronto, Canada. We find that in both cities, recent immigrants have greater levels of public transit accessibility to jobs, on average, than the overall population, but the geography of immigrant settlement is more suburbanized and less clustered around commuter rail in Toronto than in Sydney. Using logistic regression models with spatial filters, we find significant positive relationships between immigrant settlement patterns and transit mode share for commuting trips, after controlling for transit accessibility and other socio-economic factors, indicating an increased reliance on public transit by recent immigrants. Importantly, via a sensitivity analysis, we find that these effects are greatest in peripheral suburbs and rural areas, indicating that recent immigrants in these areas have more risks of transport-related social exclusion due to reliance on insufficient transit service.     

Spatial analysis of access to and accessibility surrounding train stations: a case study of accessibility for the elderly in Perth,Western Australia

Approximately one-fifth of Perth’s population is aged 60 or older. Projections suggest that this proportion will continue to increase as a result of the large number of children born after the World War II (1946–1964). Access to and accessibility around train stations for the aging population is and will become a more important issue as the elderly population continues to grow. The aim of the paper is to develop and apply a new measure of accessibility to train stations at a fine spatial scale, justified by the special circumstance of the elderly using a case study in Perth, Western Australia. Intercept surveys are used to collect data on factors affecting train station accessibility for patrons aged 60 years or older, at seven highly dispersed train stations. Overall accessibility is measured separately using a composite index based on three travel modes (walk-and-ride, park-and-ride and bus-and-ride). The results illustrate that key variables, such as distance from an origin to a station, walking or driving route directness, land-use diversity, service and facility quality, bus connection to train stations, all affect the accessibility to train stations for the elderly. This implies that improvements to these factors will improve accessibility for this population group.     

Population growth,accessibility spillovers and persistent borders: Historical growth in West-European municipalities

Lack of cross-border transport supply has repeatedly been blamed for the fact that national borders limit spatial interaction and, consequently, the growth of border regions. This study applies an accessibility approach to investigate for most municipalities in ten countries in mainland West Europe if foreign transport supply is lagging behind, and if population growth in these municipalities has been affected by the limits that national borders have imposed on market access. To do so, data describing historical population changes and road networks between 1961 and 2011 have been used. The results show that in the study area, cross-border transport accessibility was not at a disadvantage in 1961 and has since then grown even more than domestic accessibility. However, municipal population growth has depended almost exclusively on domestic market access. Processes of economic international integration in the study area are found to coincide with the growth of cross-border accessibility, but do not have a clear coincidence with the effects of cross-border accessibility on population growth.     

Perceived accessibility: What it is and why it differs from calculated accessibility measures based on spatial data

Accessibility is usually evaluated using indicators calculated from spatial data. However, perceived accessibility, defined as the perceived potential to participate in spatially dispersed opportunities, is often poorly reflected by these calculated measures. This paper sets out to explain the mechanisms that lead to these mismatches. A conceptual model is constructed to establish what factors shape perceived accessibility. A schematic framework shows that mismatches between a calculated indicator and perceptions can stem from inaccuracies in awareness as well as from inaccuracies in the measure if the measure fails to take account of the subjective evaluations of accessibility components. When evaluating the performance of land-use and transport system configurations, calculated measures based on spatial and transport data only serve as proxies for how accessibility is actually experienced. This paper argues that bringing perceived accessibility to the fore of accessibility-based planning, by acknowledging and evaluating potential mismatches with calculated accessibility indicators, will advance the evolution from mobility-based to accessibility-based planning.