This paper examines driver acceptance of mandatory ISA. This intervening system that prevents the driver from exceeding local limits runs the risk of insufficient support of stakeholders and drivers because behaviour is restrained. At the same time, the expected impact on efficiency and traffic safety might be greater than the effects of permissive systems. Measuring driver acceptance was a major objective of a Dutch field test involving 120 test drivers who used the mandatory ISA system during six weeks. The research design included three different reference groups with varying degree of ISA exposure. The major research question addressed in the paper is the acceptance level of mandatory ISA among drivers who experience the system. The related question whether acquaintance with automatically enforced speed adaptation goes with either a lower or a higher level of acceptance is discussed. The acceptance data show considerable similarities with the Hawthorne effect. It is concluded that the level of acceptance of mandatory ISA is fairly high - higher than expected - and that experience results in a higher acceptance level. (Author/publisher)
Abstract