Evaluation of 2004 Tennessee crash data reported to the MCMIS crash file

Abstract

This report is part of a series 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 incomplete. This report examines the factors that are associated with reporting rates for the state of Tennessee. MCMIS Crash File records were matched to the Tennessee Crash file to determine the nature and extent of underreporting. Overall, it appears that Tennessee is reporting 51.3 percent of crash involvements that should be reported to the MCMIS Crash file. Reporting rates vary by crash severity and vehicle type. Overall, about 93.5 percent of fatal involvements are reported, compared with 54.8 percent of injury/transported involvements, and 47.4 percent of towed/disabled involvements. Crashes involving large trucks such as tractor-semitrailers or doubles combinations were more likely to be reported than crashes involving small, single-unit trucks or buses. The reporting rate for the Tennessee Highway Patrol is 57.0 percent, while the rate for city police is 49.9 percent and the rate for sheriff’s offices is 37.8 percent. Missing data rates are not negligible for more than a few variables in the MCMIS Crash file. Certain key variables such as vehicle configuration are more than 95 percent missing. Missing data rates are also elevated for sequence of events variables, number of vehicles in the crash, and driver license class. Hazardous materials variables display some inconsistencies between data in the MCMIS file and data recorded in the Tennessee file.