A typology of accessibility measures

In order to reflect the policies and available data the starting point for accessibility measures recognises that transport is a derived demand and both the supply of opportunities and the supply of transport need to be included for each population group.

Accessibility measures fall into three main categories:

1      Decisions about the local street environment – accessibility by walking and cycling to local facilities

2      Decisions about transport investment – accessibility of public transport systems

3      Cross-sector decisions about accessibility plan delivery – access to opportunities using road and transport systems.

There are many combinations of people, activities and links that define accessibility in any individual situation. A practical approach to accessibility measurement must assist the assessor to:

·         define activities to represent quality, choice, scale, need, restrictions on availability, opening times, scheduling and other factors relating to the service provision

·         segment the population to reflect abilities and perceptions, given these are often specific to individuals or small groups

·         ensure a broad view of all transport and communication options, which reflect all aspects of modal choice, telecommunications, and quality in terms of speed, cost, prestige, security, comfort and other factors.

Where quantitative data is not available on any aspect, then the toolkit needs to utilise qualitative measures to ensure it can assist the user to make the best possible decisions. One of the greatest concerns with accessibility analysis and modelling is that it is very data hungry. Although data availability has increased very rapidly in recent years, accessibility analysis is still dominated by tools that consider mainly travel time and in some cases cost. Although it has been practical for many years to include a wider range of factors using existing data there remains a surprising lack of rigorous analysis of factors other than time and cost. Even large investments in information, ticketing, Wi-Fi, CCTV and other factors have taken place with very little analysis of priorities despite practical accessibility analysis approaches being available.

The earlier parameters can be used within the toolkit to assist users in selecting and inputting the best available data set or prompting for the collection of data where there is none available. The outputs can then ensure accessibility planners tackle all of the critical barriers to access and provide relevant information to support fund assembly and project delivery.