Karst Geurs

Ex ante evaluations of transport policy options (including infrastructure plans) are generally based on cost-benefit analyses (CBA). Accessibility changes are included in such analyses indirectly, via a utilitarian perspective. But accessibility is broader than is assumed by this perspective and also incorporates equity and related distribution effects as well as social exclusion. This paper aims to give an overview of the relevance of distribution effects and equity, and social exclusion for accessibility, based on the literature. The most important conclusions of our paper is that the two subjects are poorly addressed in transport appraisal in general, and in CBA in particular. Additional ethical theories could add value to the utilitarian perspective, egalitarian theories being a major competitor. Equity analysis is however complex because there are several types of equity, various ways to categorize people for equity analysis, numerous impacts to consider, and various ways of measuring these impacts. And such analysis requires normative judgements, in addition to simply presenting distribution effects. Several options are available to express distribution effects. Important choices to be made if such effects need to be reported relate to the unit of comparison (e.g. the household versus the individual), the indicator to be used, and the value of each unit to be compared (e.g. accessibility) for all units of comparison (e.g. households). We also conclude that CBA is not suitable for evaluating social exclusion policies. Based on this overview we propose an agenda for potential future research in the area of ethics and accessibility.

Abstract Transport appraisals in European countries increasingly address three dimensions of sustainability—economic, ecological and social. However, social impacts of transport have been underexposed in (ex‐ante) transport project appraisal, at least in the Netherlands. Firstly, this article presents a theoretical framework describing the relationships between determinants of social impacts of transport; it also provides a definition and categorization of those impacts. Secondly, the article reviews the state of the practice of national transport project appraisal in the Netherlands and the United Kingdom. The article shows that social impacts of transport investments can take on many forms and their levels of importance may vary widely, in project appraisal. The UK transport appraisal guidance includes a spectrum of social impacts through quantitative and qualitative assessments that is broader than the Dutch appraisal guidance. However, it does not cover the full range as identified in the literature. This holds, in particular, for the temporary impacts of transport investments, health impacts, social cohesion, the distribution and accumulation of impacts across population groups and social justice. All in all, it can be concluded that there is a long way to go before social impacts of transport projects are completely included in appraisals, in a way that allows us to compare them to economic and ecological effects.

In recent years there has been a significant increase of temporally variable analyses of accessibility by public transport as a result of the increased availability of open and standardized time table information in the form of GTFS (General Transit Feed Specification) data. To date, very little attention has been paid to systematically analyze the impact of temporal resolutions on the results. Different authors have applied different standards, often in an ad-hoc manner. In this study, we address the loss of precision associated with a stepwise reduction of the temporal resolution of travel time estimations based on GTFS data for the city of Szczecin in Poland. The paper aims to provide guidance to researchers and practitioners on the selection of appropriate temporal resolutions in accessibility studies. We test four sampling methods in order to analyze four different public transport frequency scenarios, three types of accessibility measures (travel time to the nearest provider, cumulative opportunities measure and potential accessibility) and seven types of destinations ranging from high to low centrality. Additionally, the impact on spatial disparities is explored using the Gini coefficient.<br/><br/>We find that a reduction of temporal resolution is associated with a decrease in precision of public transport accessibility measurement. However, with up to 5-min resolutions this reduction is negligible, while computational time is reduced fivefold, compared to a 1-min resolution benchmark. Lower temporal resolutions still provide relatively precise estimations of travel times and accessibility measures. However, further resolution reductions are associated with decreasing reductions of computational time. As a result, we argue that 15-min temporal resolution provides a good balance between precision and computational time while providing very precise estimations of Gini coefficients (errors ≤0.001).<br/><br/>A non-linear relationship is found between the public transport frequency and the loss of precision, with lower frequencies leading to a greater loss in precision. More attention should be paid to highly centralized services, in particular when analyzed using proximity and cumulative opportunities measures. Finally, the cumulative opportunities measure is found to be highly sensitive to changes in the temporal resolution and not suited for time-sensitive accessibility analysis.