Literature review of indicators, relevant for mapping accessibility in Flanders. This report defines accessibility, based on an extensive review of national and international literature, as the extent to which the land-use and transport system enables (groups of) individuals or goods to reach activities or destinations by means of a (combination of) transport modes (Geurs & Ritsema van Eck, 2001; Geurs & van Wee, 2004). Four important aspects contribute in the determination of accessibility, namely transport, land-use, policy and context. These aspects are further divided into sub aspects. To attain a theoretically sound and comprehensive presentation of accessibility, a set of indicators of accessibility should ideally take all four aspects and sub aspects of accessibility into account. In current practice, many different and incomplete definitions of accessibility are used, resulting in inadequate and partial operationalizations of the concept into indicators. This has, in turn, led to incomplete data collection. Merely considering the situation on motorways instead of the various road types and even other networks is the main shortcoming of current data collection. Vandenbulcke et al. (2009) demonstrate the mayor consequences that are implied, since incomplete and inadequate operationalization may lead to misperceptions of accessibility. The proposed indicators in this report are not exhaustive, but are a selection of most commonly used indicators in international literature that can be applied to the Flemish situation. The presented indicators are therefore not ideal. They form the basis for the final set of accessibility indicators for Flanders for which operationalization and a baseline measurement are provided in a subsequent report. Most commonly used indicators for describing the accessibility of a country or region, are mainly focused towards the transportation aspect of accessibility. This literature study shows that in current Flemish, federal and even Dutch (policy)documents indicators such as the number of vehicle hours lost on highways, average speed and travel times on highways, congestion probability on highways, the length of road networks… are preferred. Although national and international policy documents indicate the importance of aspects such as distance, time, speed, reliability, robustness, cost and convenience, current literature shows a limited operationalization of these aspects of accessibility in practice. Some of the most frequently used indicators do reflect on distance, such as the length of the networks, on time, such as vehicle hours lost, on speed, such as average travel speed, and on reliability, such as severity of congestion and congestion probabilities. Less common indicators that can be added, are: * Distance: number of kilometers traveled per person per mode and per time period, number of vehicle kilometers per mode and per type of infrastructure, average trip distance by trip purpose. * Time: number of minutes spent traveling per person and per time period, average journey time per route per time period. * Reliability and robustness: number of kilometers congestion per time and per route, I/C ratio per route and per time period, level of service per route and per time period, saturation rate per route, road section index, misery index, buffer time index, time needed to free lanes after an incident, lane length per unit area, spare capacity per route and per time period. * Costs: average travel cost per mode and per time period. Indicators with respect to comfort require additional research in terms of operationalization. This literature review represents a first and necessary step in the process of identifying a set of indicators for the visualization of accessibility in Flanders. A follow-up study will search for a suitable set of indicators that can be applied in the Flemish policy regarding accessibility. The follow-up report also seeks to operationalize the set of indicators, in which specific attention is paid towards the application of the indicators for Flanders (=baseline measurement). (Author/publisher)
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