The lighting industry has changed dramatically over the past decade. The optical system design of legacy high-intensity discharge (HID) luminaires was restricted to the lamp, refractor, and reflector design, which had limits in the distribution of the light, controls, and adaptability. Roadway luminaires have moved beyond this design methodology to include the vast possibilities presented by solid-state lighting (SSL). At present, in the form of light emitting diodes (LED), SSL uses lower energy, reduces maintenance, improves color, and can be easily dimmed and controlled.
The TRB National Cooperative Highway Research Program’s NCHRP Research Report 940: Solid-State Roadway Lighting Design Guide: Volume 1: Guidance develops more comprehensive guidelines in American Association of State Highway Transportation Officials (AASHTO)-standard format for the application of roadway lighting related to the widespread adoption of SSL, and identifies gaps in knowledge where possible future research will enhance these guidelines.