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Evaluation of Washington crash data reported to MCMIS crash file


Authors: Daniel F. Blower, Anne Matteson

This report 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. The earlier studies showed that reporting to the MCMIS Crash File was significantly incomplete. This report examines the sources of underreporting for the state of Washington. MCMIS Crash File records were matched to the Washington Police Accident Report (PAR) file to determine the nature and extent of underreporting. Evaluation of the Washington data was significantly complicated by the fact that not all of the criteria to identify cases that should be reported to the Crash file are included in the Washington PAR file. However, using reference distributions from other states, it was possible to estimate that between 37.6 percent and 53.7 percent of reportable cases are uploaded to the MCMIS Crash file. Crashes involving a fatality are more likely to be reported than crashes in which the most serious injury was an A- or B-injury. Crashes involving large trucks such as tractor-semitrailers or doubles combinations were more likely to be reported than crashes involving single-unit trucks or buses. Crashes covered by the Washington State Police were more likely to be reported than those covered by either county sheriffs or local police departments. Missing data rates are low for most variables, although the important body type variable is almost all missing data, and rates are high for some hazardous materials variables. Inconsistencies were identified for some variables. In particular, the vehicle type description in the PAR file differs greatly from the corresponding vehicle configuration variable in the MCMIS Crash file.

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