Evaluation of California crash data reported to MCMIS crash file

Abstract

This document is part of a series of reports evaluating the data reported to the Motor Carrier Management Information System (MCMIS) Crash File undertaken by the Center for National Truck and Bus Statistics at the University of Michigan Transportation Research Institute. Earlier studies showed that reporting to the MCMIS Crash File was significantly incomplete in other states. This report examines the sources of underreporting for the state of California. MCMIS Crash File records were matched to the California Police Accident Report (PAR) file to determine the nature and extent of underreporting. Overall, California submitted 52.6% of its reportable crash involvements to the MCMIS Crash File in 2003. Reporting rates varied by vehicle type, crash severity, and reporting agency. Reporting rates are 71.3% for fatal crashes, 53.2% for injury cases, and 51.9% for tow/disabled accidents. Where specific truck type could be determined, two-axle trucks are reported only 50% of the time, while three-axle trucks and truck tractors each have an 85% reporting rate. Buses are only reported 13.3% of the time. CHP agencies had a reporting rate of 72.0%, compared with 5.7% for police departments, and 6.7% for sheriff’s offices. Since recognizing and accurately coding reportable cases is the responsibility of the officer at the scene of the crash, inadequate training may be an issue. It also appears that heavy caseloads may explain why a few jurisdictions in the densest population areas have lower overall reporting rates. Although California’s data collection system is consistent with MCMIS reporting requirements, the use of more than one vehicle type variable and the lack of sufficient documentation may lead to incorrect identification of reportable vehicles.