Project Goal

The aim of this project is to determine whether warning devices meaningfully impact crash-relevant aspects of human performance in the presence of a stopped commercial motor vehicle, and if so, how, and to what extent.
 

Background

The fundamental intention of safety regulations requiring the use of warning devices to mark the location of a stopped commercial motor vehicle is to reduce crashes. Presumably, such devices achieve this benefit through a straightforward mechanism: by attracting motorists’ attention to the position and orientation of the stopped vehicle, thereby facilitating earlier detection of the vehicle, and consequently, a more effective response to its presence.

Producing quantitative evidence of such a benefit, however, is challenging, in that ethical considerations preclude a meaningful comparison of crash frequency in the context of a scientific experiment. Consequently, the effects of warning devices must be inferred from the extent to which they modify aspects of human performance which are conceptually linked to crash avoidance. FMCSA has never conducted experimental research on the impacts of warning devices, and prior research by external parties investigating the effects of warning devices indirectly through human performance metrics has yielded inconsistent results.

As a result, there is presently no consensus as to whether, how, when, and to what extent warning devices impact crash-linked, safety-relevant behaviors in passing motorists. Despite these inconclusive findings, FMCSA nonetheless requires that warning devices be carried in all commercial motor vehicles and that they be deployed in the situations and manner described in the corresponding safety regulations.

This approach presents challenges of its own. For instance, FMCSA has occasionally received requests from parties desiring to use alternative warning devices, e.g., on the basis that they are simpler to use or deploy. Without sufficient data regarding the effects of warning devices on motorist behavior or crash reduction, FMCSA lacks a quantifiable standard – i.e., a baseline level of safety – against which an alternative device might be compared.
 

Summary

The Research Division of Federal Motor Carrier Safety Administration (FMCSA) plans to perform an assessment of drivers’ detection of stopped commercial motor vehicles and the nature and efficacy of their responses to those vehicles, including in the presence and absence of warning devices required by 49 CFR § 393.95 and deployed in accordance with 49 CFR § 392.22.

To that end, FMCSA will conduct an on-the-road study testing whether warning devices meaningfully impact crash-relevant aspects of human performance in the presence of a stopped commercial motor vehicle, and if so, how, and to what extent.

The information obtained from this study will potentially inform FMCSA and the public as to the baseline effects of warning devices on driving performance and crash avoidance behaviors.
 

Contractor

Virginia Tech Transportation Institute