USING LOGSUM MEASURES FOR TRANSPORT EQUITY ANALYSIS: A CASE STUDY FOR LONDON
Aruna Sivakumar, Imperial College London, Malvika Dixit, Imperial College London
This paper compares different aggregate and disaggregate measures of accessibility in their implications for equity analysis of transport policy.
Within the UK there is a focus on increasing accessibility to jobs and services specifically for people in vulnerable groups such as senior citizens, low income households etc. The aggregate level accessibility measures currently in use cannot be aggregated based on individual characteristics and hence cannot specifically identify accessibility issues for these vulnerable groups. This paper explores the suitability of using logsum measures for transport equity analysis in the context of work commute trips, and the impact of including individual characteristics within these measures of equity.
The methodology adopted to achieve this aim consists of three steps: (1) Develop logsum measures for accessibility to jobs within London – with and without incorporating individual characteristics; (2) Compare accessibility patterns obtained using the two measures to explore the causes of existing inequalities; (3) Establish the suitability of the two measures for equity analysis of transportation and land-use policies. Different dimensions of equity analysis were explored by aggregating accessibility based on geographical location and socio-demographic characteristics. Hypothetical policy scenarios were also implemented to illustrate the use of these measures for equity evaluation of policies.
The findings suggest that logsum measures do not add significant value when aggregated across large geographical zones, but can provide useful insights for equity analysis across socio-demographic segments. It was also found that individual characteristics are often responsible for accessibility variations and ignoring them will overestimate equity. For policy evaluation using the two measures, transport policies were found to be more sensitive than land-use policies to the inclusion of individual characteristics in the equity measure.
With the focus of accessibility planning in the UK on addressing the concerns of vulnerable groups the current study demonstrates that (i) disaggregate level measures like the logsum can be very useful in identifying the distributional impacts for these socio-demographic groups of interest - the logsum measures can be constructed to specifically capture the issues concerning these vulnerable groups; and (ii) when looking at variations by socio-demographic segments, it is important to consider the impact of individual characteristics on accessibility, especially for evaluating transport policies.
Association for European Transport