Evaluation of Michigan crash data reported to MCMIS Crash File

Abstract

This is one of a series of papers presenting the results of an evaluation of 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. This report examines the sources of underreporting for the state of Michigan. In 2003, there were 5,911 crash involvements in Michigan that were reportable to the MCMIS Crash file. 4,926 involvements were reported for that year, for a reporting rate of 73.7%. 303 of the cases reported to the Crash file did not meet the reporting criteria. 92.4% of fatal involvements were reported, 73.1% of qualifying injury crash involvements, and 73.4% of crashes with a towed, disabled vehicle. Unlike many other states, in Michigan reporting officers are responsible to identify qualifying vehicles (trucks, buses, and vehicles placarded with hazardous cargo), but cases meeting the severity criteria are selected centrally. This system likely partially explains the overall pattern of underreporting. Underreporting also is related to the time of year, indicating delays in providing the data. Reporting rates also varied by jurisdiction, with larger communities with more cases having higher rates of underreporting. Data quality is also reviewed. In certain variables, data in the Michigan police report file differed from that in the Crash file for some cases. Some inconsistencies were also noted between cargo body and vehicle configuration in the police report file and in the MCMIS Crash file.