Estimation of travel times on urban freeways under incident conditions

Travelers on urban freeways are interested in knowing how long it will take them to reach their destinations, especially under bottleneck, congested, and incident conditions. Travel time information is important for advanced traveler information systems (ATIS) applications and for assessing the performance of the transportation network. Though many advances have been made in the field of traffic engineering and intelligent transportation system applications, practical travel time estimation procedures for ATIS applications under incident conditions are lacking. An algorithm for travel time estimation on urban freeways for ATIS applications under incident conditions is presented. The algorithm is based on point estimates of traffic variables obtained from detectors placed on every link of the freeway network. The output required from the detectors is flow and occupancy aggregated for a short time interval (5 min). The system for travel time estimation is based on traffic flow theory rather than on statistical methods. The travel times calculated using this system are compared with the results obtained using the FHWA microsimulation computer package CORSIM in the Traffic Software Integrated System (TSIS) Version 5.0. The algorithm results are found to be reasonable and accurate compared with CORSIM results.