Evidence from the USA shows built environments and travel behaviour are closely related (Handy and Clifton 2001). Policy aims which emphasise neighbourhood accessibility have the greatest potential for maximising interaction between people and activities within communities. Where people can access opportunities closer to where they live they do so. They also tend to use slower modes.
Improving access is implicit in most transport planning and infrastructure investment. However this implicit treatment is sometimes insufficient for transport planning since:
· There can be unintended consequences from transport investment. For example, when a road is upgraded to a rural community, the shops and services in the rural community often close (Scottish Executive 2001a) resulting in reduced accessibility for the rural area for some trip purposes.
· The impacts of the change are different by population group and area so distributional effects need to be understood (UK Treasury 2003).
· There is a close relationship between transport supply and demand so both accessibility and mobility need to be considered (Hansen 1959).
· Public acceptability is critical, but technical concepts such as speed/flow relationships and supply/demand interaction are poorly understood by the travelling public. If it is proposed to restrain the supply of opportunities for one mode to improve accessibility overall (eg a pedestrianisation scheme), then it is necessary to describe the impacts on people rather than modes to ensure broad support for the proposal (Halden 1996).