Turner-Fairbank Highway Research Center

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Effects of a Towaway Reporting Threshold on Crash Analysis Results

Product Type

Journal Article


Charles V. Zegeer, Herman F. Huang, J. Richard Stewart, Ron Pfefer and Jun Wang



Full citation

Charles V. Zegeer, Herman F. Huang, J. Richard Stewart, Ron Pfefer, and Jun Wang. Effects of a Towaway Reporting Threshold on Crash Analysis Results, Transportation Research Record 1635, TRB, National Research Council, Washington D.C., 1998


The effects on future data analysis capabilities and results should states convert to a towaway and above crash-reporting threshold are quantified. The results from the four states used in the analysis (Illinois, Michigan, Minnesota, and North Carolina) revealed that only 51.7 percent of the crash data would be included using a towaway threshold. Only 33.7 percent would be included using an injury threshold. In general, a towaway threshold would exclude more crashes on urban street than on rural roads. For most road classes, 40 to 60 percent of crashes would be excluded. A towaway threshold would result in greatly underestimating the occurrence of certain crash types, particularly rear-end, sideswipe, parking, and animal crashes. Run-off-road and angle/turning crashes would also be affected considerably. Using a towaway criterion will seriously affect researchers' ability to conduct meaningful evaluations of roadside appurtenances, such as guardrail, breakaway signs and poles, crash cushions, and various median treatments. For most vehicle types, only 30 to 60 percent of crashes would be included under a towaway threshold. Technological, institutional, and organizational strategies for improving crash-reporting thresholds are suggested.

Available From

Transportation Research Record 1635

Link To Journal Article

Link not available.


Reporting Threshold
Crash Analysis

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