Motorist Information Systems: An Introduction

Motorist information systems enhance drivers’ knowledge of the situation in road networks, and thus improve driver’s decision-making (Ben-Akiva et al., 1991; Bonsall et al., 1991; van Berkum and van der Mede, 1993). However, it is far less well understood whether and to what extent the interaction between the drivers themselves and the information and the drivers may reduce potential beneficial effects of these new technologies. A few models have been developed in order to assess the potential of motorist information systems. Whether these are able to capture the main characteristics of these systems is unclear (Watling, 1994). Using simulation experiments, Mahmassani and Chen (1991) and Mahmassani and Jayakrishnan (1991) found that if more than 20 per cent of the drivers are equipped with the motorist information system, the negative effects due to concentration and overreaction (Ben-Akiva et al., 1991), may begin to outweigh the beneficial effects. Concentration takes place if the information reduces the variations among drivers, increases uniformity of perceptions of network conditions and thus increases congestion. Overreaction occurs if drivers do not fully take into account the responses of other drivers provided with the same information, thereby shifting the congestion from one road to another. In these circumstances Mahmassani and Jayakrishnan (1991) argued that provision of coordinated information is necessary.