What happens when mobility-inclined market segments face accessibility-enhancing policies?

Improvements in accessibility are increasingly suggested as stategies leading to a reduction in vehicular travel, congestion, pollution and their related impacts. This approach assumes that individuals, if offered an opportunity, are likely to reduce their travel. It also assumes that accessibility-enhancing land-use changes will increase transit and non-motorized trips in lieu of automobile usage. However, there are numerous indications that people engage in excess travel and are not necessarily inclined to reduce it. This paper presents a number of hypotheses on the reasons for excess travel and the relationships among attitudes toward travel and responses to accessibility-enhancing strategies. It suggests that different market segments are likely to respond to policy measures in different ways. In particular, if a large segment of the population prefers mobility over the reduced travel offered by accessibility improvements, then such policies will be less effective than anticipated.