Decision support system for locating traffic information dissemination sites along freeway corridors

Dynamic route guidance systems which are products of the Intelligent Transportation Systems (ITS) Technology have been reasonably useful in guiding motorists from their origins to destinations. In general, transportation networks could be used more efficiently if dynamic route guidance information could be provided to motorists at all relevant locations along freeway corridors. This is however not possible, particularly because of financial constraints. It is therefore imperative that information be provided to motorists at locations where it will be of maximum benefit.

The objective of this research is to develop methodologies and computer models for estimating utility of motorist information at different locations along freeway corridors. Such models will be very useful in guiding transportation professionals to optimize resources when providing guidance information to motorists. The methodologies have been developed based on both recurrent and non recurrent traffic congestion situations. The methodologies assume that motorists behave rationally and will divert from congested freeways to uncongested arterials based on the user equilibrium traffic assignment criteria. The utility of information estimation has however been based on total system time savings. Computer models have been developed based on the methodologies using the C++ programming language. Nonetheless, because the computer models have been developed based on historical traffic data, they have been validated using real time simulation models developed with the SIMSCRIPT II.5 programming language. The validation process proved reasonably successful.

Many factors which include traffic volumes on alternate arterial routes to a given freeway link, the number of alternate routes to the freeway link especially under recurrent traffic congestion conditions, link lengths, volume of traffic on the freeway link and incident history in the case of non recurrent congestions influence the utility of information. With the particular networks investigated in this research however, the results indicate volume of traffic on the freeway links as the most influencing factor, since freeway links with relatively high traffic volumes tend to have relatively high utility values. The reason for this is probably because of the small size nature of the networks used, hence as a result all the freeway links tend to have only one or two alternate routes and the traffic volumes on the arterial links also do not differ significantly. The freeway link volumes therefore become the dominating factor in influencing the information utilities.