Study of present-day LED brightness and corresponding rear signalling concepts (LED optimization)

  • Published: NHTSA (National Highway Traffic Safety Administration, 2009)
  • Authors: NHTSA (National Highway Traffic Safety Administration)
  • Date Added: 25 Jan 2014
  • Last Update: 25 Jan 2014
  • Format: pdf


To develop optimised rear brake lighting signal configurations using present-day lighting assemblies, but with LED (light-emitting diode) technology.


Work under this study included a laboratory component to quantify the brightness levels of various LED lamps, and a data collection component using human participants intended to determine optimum flash frequencies, brightness levels, and signal patterns (e.g., simultaneous versus alternating flashing).

Key Findings:

  • Compared with the results of earlier tests of enhanced rear signals with very high brightness levels (1376 cd), the LED assemblies evaluated here are much below this. However, it should be possible to compete favourably with the incandescent units (at least, on axis) by using multiple units.

  • One important finding is that the optimum flash frequencies for LED-enhanced brake signal lights are slightly higher than for incandescent lamps. This appears to occur because there is no trade-off of desired frequency and rise/fall times for LEDs, which are relatively instantaneous.

  • This research demonstrated that flashing all lights simultaneously or alternately flashing is a promising signal for use in enhanced brake light applications.


LED (light-emitting diode), brightness, attention getting, rear signalling, brake lights.


Traffic safety facts release from NHTSA’s Vehicle Safety Research