I-880 Field Experiment: Data-Base Development and Incident Delay Estimation Procedures

Abstract

The collection and processing of field data on freeway incidents and operating conditions are described, and the development and application of a methodology for estimating incident delays are presented. The data were collected on a section of the I-880 freeway in the San Francisco Bay Area before and after the implementation of freeway service patrols (FSPs). Incident characteristics were obtained through observations of probe vehicle drivers traveling at an average of 7-min headways. Travel times were obtained from the specially instrumented probe vehicles. Speeds, flows, and occupancies at 1-sec intervals were collected from closely spaced loop detectors on the freeway main line and the ramps. Software was developed to process the data and create a computerized data base. The I-880 data base consists of 276 hours of field data that are uniquely linked to provide a complete representation of the freeway operating conditions at the test site. Improved procedures for estimating incident delay and other performance measures were developed and incorporated into the data processing and analysis software. The delay estimation methodology and field data were used to determine the benefits of the FSPs. The results indicate that the FSP is a cost-effective incident management measure at the study section.

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