In September, 2005 FMCSA initiated development of a prototype enhanced rear signaling system for use on commercial motor vehicles (CMVs). The system incorporates countermeasures that were developed in Phase I of this project. The system was evaluated by installing it on a test truck and by observing the behavior of drivers in real-world conditions. Based on the analysis of following driver behavior, the system showed that there are possible benefits to this system, or elements of this system, when used on CMVs. FMCSA is now considering conducting a field operational test (FOT) to further explore this system.

The countermeasures identified in Phase I include: (1) LED brake lamps with an ambient light sensor to make the lamps brighter in direct sunlight and more conspicuous in bright ambient light, (2) brake lamps that are activated by engine braking to address the increasing use of jake brakes in CMVs, (3) additional conspicuity markings that create a more accurate perception of the truck position for following drivers, (4) a sensor system that detects and tracks a following vehicle and sounds a focused audio signal and illuminates a traffic clearing lamp when the vehicle is following too closely or approaching at too high a rate of speed.

Phase III of the Enhanced Rear Signaling project will entail lab, simulator, track, and jury tests to ascertain the best configuration and combination of countermeasures to be used in a large scale FOT. In addition, a large scale, 18-month FOT will be designed. The research will entail exploration of most effective photometric characteristics of the enhanced brake lamps, comparison of existing required retro-reflective markings with the octagonal retro-reflective markings developed in Phase I, and lab/simulator and/or track tests of changes in closure rates with the prototype and without.

Phase IV of the Enhanced Rear Signaling project will execute a large-scale field operational test to analyze the benefits of the prototype system developed in Phase II. Its goal will be to determine the effectiveness of the specific components of the system and develop support for any potential rulemaking action that NHTSA may choose to undertake.