ACCESSIBILITY MEASURES COMPARED IN AN ANALYSIS OF THE IMPACT OF THE M25 LONDON ORBITAL MOTORWAY ON BRITAIN

A number of established methods exist for measuring levels of accessibility over space. Most notable are those based on market potential and access cost. This research is concerned with the comparison of these methods and the results that they produce in a particular empirical context. Accessibility costs for HGVs by road are measured for 1980s Britain with special reference to the M25 London Orbital Motorway. Specific calculations are made for accessibility which include and exclude the road and are dependent on an exogenously derived route minimisation procedure. These are assumed to represent the postroad and preroad situations, respectively. The findings point to significant differences in the results depending on the method chosen. This is contrary to previous research in the field.