Commuter Response to Traffic Information on an Incident

Problem

How is traffic information obtained by commuters? And how is travel behavior affected by information about congestion on a major freeway? This report is part of a larger evaluation of the TravInfo travel advisory telephone system Field Operational Test.

Method

A travel corridor was selected to meet several criteria, such as availability of good alternate routes, transit alternatives, and updated traffic information. Caltrans license plate surveys provided addresses of travelers in that corridor. They were contacted via mail, and a panel of around 1100 commuters agreed to participate. A major incident on July 10, 1997 created congestion meeting certain criteria, including location within the corridor under study, having an effect lasting at least thirty minutes, and blocking at least one lane. On the evening of the incident and for four days following, phone interviews were completed with 106 of the 563 panel members who regularly travel in that corridor

Findings

Commuter travel behavior is largely unaffected by individual incidents of congestion. Even when commuters obtain traffic information, they don't always change their behavior in response to it.

Three-quarters of the commuters interviewed had flexible arrival times at work. Only 51.4% obtained traffic information, and of those 70.8% did not change their departure time, route, or mode. Most of them learned about the incident from commercial radio broadcasts, and 47.2% of these respondents were unsure as to whether the information saved them travel time.

50% of respondents would not make a greater effort in the future to obtain traffic information during their commute, and 65.7% of them would not do so before their commute.

Overall, 13.3% of the travel changed. There was a greater impact on departure time and route change than on mode shift to mass transit.