Evaluating Relationships between Perception-Reaction Times, Emergency Deceleration Rates, and Crash Outcomes using Naturalistic Driving Data

Perception-reaction time (PRT) and deceleration rate are two critical factors in stopping sight distance (SSD). Since SSD is a critical design criterion (it controls vertical curve design and horizontal sightline offsets), the values of PRT and deceleration rate used in design have large impacts on both the safety and costs of the roadway system. PRT and deceleration rates are also used in crash reconstruction, which can impact the outcomes of lawsuits and tort liability. Current American Association of State Highway and Transportation Officials (AASHTO) SSD guidance related to PRT and deceleration rate is provided in A Policy on Geometric Design of Highways and Streets (herein referred to as the Green Book). These values are based on 90th percentile PRT and 10th percentile deceleration rate values from experiments that were completed in Texas in the mid 1990’s. However, these experiments lacked real-world distractions that drivers are subject to, were limited in the age range and abilities of drivers, did not test a wide variety of initial speeds and lighting conditions that may impact PRT and deceleration rates, and did not account for potential correlations between the PRT and deceleration rates. Thus, the values from these experiments may not be applicable in real-world scenarios. Recent research has used driving simulators and naturalistic data from the 100-car naturalistic driving study to evaluate PRT. However, the sample sizes and conditions accounted for were limited. Also, the relationship between PRT and deceleration rate was not accounted for. Little research has been done that evaluates average emergency deceleration rates. The Strategic Highway Research Program 2 (SHRP2) recently implemented a multi-year naturalistic driving study (NDS) data collection effort that included over 3,400 drivers across the United States in an effort to address the role of driver performance and behavior in traffic safety. This effort developed a database that researchers can use to assess driver characteristics and behaviors. This is a potential source that could be used to assess and develop models of the relationships between PRT and emergency deceleration rates. Given that data are available for crashes and near crashes, evaluation of the differences in PRT and deceleration rates for crash and near crash events may also reveal interesting differences that can be used to prevent crashes in the future. There are likely multiple factors that influence the relationship between PRT and deceleration rate. The deceleration rate a person is likely to select (i.e., the intensity of brake application) in braking situations is likely to depend on the level of risk the driver perceives. Thus, there is potential that PRT has a direct impact on emergency deceleration rates. Large values of PRT may occur due to inattentiveness, yet the driver may brake harder due to an impending collision when compared to a shorter PRT for the same situation. Conversely, attentive drivers with long PRT may have low deceleration rates if they judge the conflict to be low risk (i.e., there is little urgency for either PRT or braking). Thus, high PRT may be associated with high deceleration rates when drivers are inattentive while attentive drivers are likely to have low PRT and high deceleration rates (for high risk situations) and high PRT and low deceleration rates for low risk situations. Understanding the relationship between PRT and deceleration rate can improve transportation engineers understanding of human factors related to SSD, leading to improved design guidance and safer roadways. It could also improve crash reconstruction and the ability to determine what happened at crashes. Therefore, a study is needed to evaluate (1) the differences in PRT and deceleration rates between crash and near crash events and (2) the relationship between PRT and deceleration rates. The results of this research could be used by transportation agencies to improve design guidance. The results could also be used in crash reconstruction and for developing policies aimed at reducing the number and severity of crashes that occur on and near the roadway.


  • English


  • Status: Completed
  • Funding: $180258
  • Contract Numbers:


  • Sponsor Organizations:

    Research and Innovative Technology Administration

    Department of Transportation
    1200 New Jersey Avneue, SE
    Washington, DC  United States  20590
  • Project Managers:

    Kline, Robin

  • Performing Organizations:

    South Dakota State University, Brookings

    Box 2201, AD 130
    Brookings, SD  United States  57007
  • Principal Investigators:

    Wood, Jonathan

  • Start Date: 20161213
  • Expected Completion Date: 20180731
  • Actual Completion Date: 20180125
  • Source Data: MPC-521

Subject/Index Terms

Filing Info

  • Accession Number: 01619664
  • Record Type: Research project
  • Source Agency: Mountain-Plains Consortium
  • Contract Numbers: DTRT13-G-UTC38
  • Files: UTC, RiP
  • Created Date: Dec 21 2016 1:22PM