Evaluation of enhanced brake lights using surrogate safety metrics. Task 2 & 3 Report: Development of rear signaling model and work plan for large scale field evaluation.

This report documents efforts undertaken as part of a larger program of research involving a series of inter-related studies and research projects intended to reduce the frequency and severity of rear-end crashes via enhancements to rear-brake lighting. It outlines current efforts leading to the development of a rear signaling model to estimate the relative safety benefits of various enhanced braking signal approaches on the incidence of rear-end crashes, as well as the development of a detailed work plan for conducting a Field Operational Test of candidate rear signaling systems. This preliminary model is a first effort designed to see if enhanced rear signaling systems can provide safety benefits. This model is not comprehensive, nor does it model any of the system costs. The results from this preliminary model found that use of brake signal configurations which simultaneously flash the brake lamps (both outboard and CHMSL units) at 5 Hz were found to be effective, reducing the crash rate by as much as a 5.1% (95% confidence interval: 3.5%-6.7%), equivalent to 21,723 fewer annual rear-end crashes. The model also found that effectiveness of the simultaneous flashing signal was moderated by both 1) signal luminance (and brightness) and 2) activation, or triggering criteria. Additional efforts are needed to increase model reliability by gathering additional data to populate model parameters, and to validate model outputs to ensure predictions are generally reflective of real-world performance. A research work plan is also presented for implementing a large-scale Field Operational Test intended to evaluate the real-world effectiveness of one or more rear signaling system implementations. (Author/publisher)