Information Provision in Road Transport with Elastic Demand. Journal of Transport Economics and Policy 30,2:117-136

Congestionseverelyaffectsmostmetropolitan areasaroundthe world. Numerous instru-ments to tackle congestionhave been studied in the past: electronic road pricing, fuel taxation, regulatory parking policies, improving public transport, and so on. Another instrument,widelyviewedto be ableto relievepartof the congestionproblem,is the use ofnew informationtechnologies in transport networks (theDRIVEland II programmes ofthe EuropeanCommunity andtheIntelligent Vehicle Highway Systems(IVHS)efforts in theUnitedStatesareexamples). Informationprovisiontodriversis believedtoimprove theirknowledgeofthe trafficsituationontheroadsandthusto improvedrivers ' decision-making (Ben-Akivaet al., 1991; Bonsall. 1992). Unfortunately, the real picture of the effects of information provision to drivers is less clear than such intuitive reasoning suggests.Atanaggregatelevel,theimproveddecision-making mightimplythatinforma-tion will direct traffic flows to the user equilibrium (Emmerinket al., 1995a;Wardrop, 1952),in otherwords,a situationcharacterised bydriveroptimaldecisions. However,the inequality between Wardrop's first (user equilibrium) and second (system optimum) principles in congestedsituations (Sheffi, 1985) indicates that informationprovided t