Accessibility (or just access) refers to the ease of reaching goods, services, activities, and destinations, which together are called opportunities.
Accessibility is almost always measures how long it takes to reach a destinations, or rather how many destinations can be reached within a certain amount of time. However, different tools and evaluations vary in the way they measure first and last mile, the types of destinations they include, population segmentation analysis, and the mechanisms used for counting destinations.
Accessibility vs. Mobility
Transit systems have been increasingly focused on accessibility when evaluating their systems and new projects. Although accessibility has always been a chief goal of transit, past measures have tended to focus on mobility, looking at number of people who can access the transit system, system capacity, and line speeds. While improvements in service strengthen the transit system, these measures do not evaluate whether people have access to important destinations. Fast transit lines reaching many may nevertheless fail to connect people to job centers, grocery stores, or schools. Far reaching transit systems may force multiple transfers to reach a destination, such that the trip becomes unreasonable long. Accessibility directly addresses these questions by measuring people's ability to reach desired destinations.
- Accessibility for Transportation Planning: Measuring People’s Ability to Reach Desired Goods and Activities. 27 February 2017. Todd Litman. Victoria Transport Policy Institute. http://www.vtpi.org/access.pdf