Evaluation of Enhanced Brake Lights Using Surrogate Safety Metrics: Task 2 & 3 Report

Of the brake signal configurations tested, those 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%, equivalent to 21,723 fewer annual rear-end crashes; these signals were also found to impact crash severity levels.

https://www.nhtsa.gov/sites/nhtsa.gov/files/811329.pdf