Missouri Highway Safety Manual Recalibration

Project status


Start date: 04/18/16
End date: 03/30/18


Principal investigator:

About the research

The Highway Safety Manual (HSM) is a national manual for analyzing the highway safety of various facilities, including rural roads, urban arterials, freeways, and intersections. The HSM was first published in 2010, and a 2014 supplement addressed freeway interchanges. The HSM incorporated the safety modeling results from several National Cooperative Highway Research Program projects that used data from various states across the nation. The HSM recommended that individual states calibrate the HSM to local conditions on a regular basis. An initial statewide calibration for Missouri was finalized in 2013. The current recalibration effort builds upon the previous calibration and is designed to keep the calibration values up to date with the most current crash data and calibration methodologies. The current effort also involves the development of crash severity distribution functions so that crash frequencies can be estimated according to the severity categories of fatal, severe injury, minor injury, and property damage only. HSM calibration is a labor-intensive effort that requires the collection and use of detailed data such as road geometrics, traffic volumes, traffic signalization, land use, and crash frequency and severity. This report documents the details of the methodology employed for facility site selection, data collection, data processing, calibration, and severity assignment. Sixteen facility types were calibrated. These included rural two-lane segments with the related three-leg and four-leg intersections; rural multilane segments with the related three-leg and four-leg intersections; urban two-, four- and five-lane arterial segments; urban and rural four-lane and urban six-lane freeway segments; urban three- and four-leg signalized intersections; and urban three- and four-leg unsignalized intersections. The calibration results indicated that the HSM predicted Missouri crashes reasonably well, with the exception of a few site types for which it may be desirable for Missouri to develop its own safety performance functions in the future.


Report: Missouri Highway Safety Manual Recalibration (6.19 mb pdf) May 2018



  • Midwest Transportation Center
  • Missouri Department of Transportation