ESTIMATION OF CURRENT CAPACITY: AN EXPLORATIVE LITERATURE STUDY

Dynamic traffic management refers to the management of traffic demand and supply based on information about current and road-specific traffic conditions. Essential to dynamic traffic management is knowledge about current capacity. Current capacity is defined as the capacity of a road given the prevailing roadway, traffic and control conditions (weather, light and traffic composition). For dynamic traffic management it is necessary to have an on-line procedure for the estimation of the capacity. The Transportation and Traffic Research Division of Rijkswaterstaat has commissioned the TNO Institute for Spatial Organization and the department of Civil Engineering of the Faculty of Public Administration of the University of Twente to perform a literature study on this subject. The literature study showed that currently three categories of methods exist for the estimation of capacity: (1) Methods based on the distribution of vehicular headways; (2) Methods based on the fundamental diagram; (3) Other methods. The literature study did not come up with operational and validated procedures. However, based on previous work, three on-line estimation procedures which seem very promising have been developed. One method is a modification of an approach which is based on the distribution of vehicular headways which has been used at the Technical University of Delft. The second method allows for an intensity dependency of the distribution of vehicular headways. The third promissing method is an extension of the McMaster University incident detection algorithm which is based on the fundamental diagram of traffic flow. (Author/TRRL)