Validation of Roadside Crash Injury Metrics in Real World Crashes (Correlation of Actual Injury Outcomes to Those Predicted During Crash Testing)

The methods used to evaluate injury risk in roadside hardware crashes were developed in the 1980s and very likely outdated. The advancement of vehicle designs (i.e., vehicle crumple zones, seatbelts, frontal and side airbags, etc.) have resulted in significant changes over the last three decades. In frontal crashes, the flail-space crash injury metric is now too conservative considering that occupants are now required to wear seat belts, airbags are used as supplementary restraint systems, and vehicles have crumple zones, all specifically designed to provide controlled ride down decelerations. In contrast in side crashes, the flail space model, which does not account for intrusion, may have the opposite problem and not be sufficiently conservative. The simplified point mass, flail-space model (FSM) was introduced in 1981 by Michie and is currently used in the United States Manual for Assessing Safety Hardware (MASH) crash test procedures to assess vehicle occupant injury risk in roadside hardware crash tests. Similar Canadian, Australian and New Zealand crash test standards also use the FSM. The European procedures use a variation of the FSM in conjunction with the Acceleration Severity Index (ASI) to gauge occupant injury risk. Both metrics are used in roadside crash tests as a substitute for an instrumented anthropometric crash test dummy (ATD). Using an ATD in MASH certification compliance testing would significantly increase the cost of crash testing to around 40 percent if not more, increasing the cost of safety hardware. Despite long-term usage to evaluate occupant risk in full-scale crash tests of roadside safety hardware, there is little information correlating either FSM or ASI to occupant injury. In addition, FSM was developed in an era when few drivers wore seat belts, airbags were still a rarity, and crumple zones in vehicles had not yet been developed. FSM predictions are hence unrepresentative of the injury risk experienced by drivers in 2017. ASI is newer and was designed for belted occupants, but has not been validated against U.S. occupants in the current fleet. In addition, both FSM and ASI are acceleration-based measures which are better suited to head and chest impacts. They are less than ideal for predicting the risk of leg injuries, such as those injuries observed in some end terminal collisions. Also, neither metric is suited for predicting injury in crashes where the occupant compartment is compromised, including broken side windows in rigid and semi-rigid barrier impacts and A-pillar cutting that can occur in crashes with cable barrier. This project will seek to compare the current MASH occupant risk procedure predictions with real world crash events where longitudinal and lateral decelerations have been measured and with results from instrumented ATD’s placed in current barrier impacts. Alternative vehicle-based methods of determining occupant injury risk will also be evaluated. The anticipated result would be revised MASH occupant risk tolerance values and/or an improved method of determining occupant injury risk in roadside hardware crash tests. Accomplishment of this objective shall require the following tasks, at a minimum: (1) synthesis of engineering rationale for FSM, ASI, and other Vehicle-Based Injury Criteria to include injury biomechanics basis, computational effort, and practicality; (2) determination of data sources for validation of roadside crash injury metrics; (3) correlation of real-world injury outcomes to those predicted by the FSM, including correlation by body region, and performance of FSM in frontal vs. side crashes; (4) correlation of real-world injury outcomes to those predicted by other vehicle-based injury criteria and determination of body region as well as the performance of each in frontal vs. side crashes; (5) ranking of FSM and other vehicle-based injury criteria by correlation to real-world injuries; and (6) proposal of MASH injury criteria and limits for incorporation in an updated MASH.


  • English


  • Status: Proposed
  • Funding: $400000
  • Contract Numbers:

    Project 17-90

  • Sponsor Organizations:

    American Association of State Highway and Transportation Officials (AASHTO)

    444 North Capitol Street, NW
    Washington, DC  United States  20001

    National Cooperative Highway Research Program

    Transportation Research Board
    500 Fifth Street, NW
    Washington, DC  United States  20001

    Federal Highway Administration

    1200 New Jersey Avenue, SE
    Washington, DC  United States  20590
  • Project Managers:

    Harrigan, Edward

  • Start Date: 20180619
  • Expected Completion Date: 0
  • Actual Completion Date: 0

Subject/Index Terms

Filing Info

  • Accession Number: 01672551
  • Record Type: Research project
  • Source Agency: Transportation Research Board
  • Contract Numbers: Project 17-90
  • Files: TRB, RiP
  • Created Date: Jun 18 2018 3:03PM