As an initial step in developing maintenance guidelines for LED traffic signals, this project developed a process for determining when LED traffic signal heads should be replaced.
The report has been published as NCHRP Web-Only Document 146: Replacement Processes for Light Emitting Diode (LED) Traffic Signals.
Task 1. Synthesize existing human factors research relevant to the visibility of traffic signals, updating it as appropriate for LED performance. Describe further research that could be beneficial to the industry. Submit a task paper within 3 months of the contract start.
Task 2. Perform studies to correlate field measurement of traffic signal visibility to laboratory measurement.
Task 3. Describe failure modes for LED traffic signals, their impacts on the visibility of a signal head, and their impacts on test procedures.
Task 4. Develop a process for determining when LED traffic signal heads should be replaced. It should be sensitive to local geographic and weather conditions.