Roadway lighting sources are being converted from high pressure sodium (HPS) and other high-intensity discharge (HID) luminaires to light emitting diode (LED) luminaires because LEDs are generally more energy efficient and may offer better visibility. LEDs with a correlated color temperature (CCT) greater than 3000K often have higher blue content in their spectrum (460 to 480 nm) than HPS lamps. Light in this wavelength affects the production of the hormone melatonin, which regulates the human circadian rhythm. In June 2016, the American Medical Association (AMA) issued a report (The Council on Science and Public Health Report 2-A-16, Human and Environmental Effects of Light Emitting Diode (LED) Community Lighting) noting that roadway lighting with higher blue content, such as the light produced by LEDs with higher CCTs, could adversely suppress melatonin and affect the sleep health of people exposed to it. However, a link between melatonin suppression and LED lighting at roadway levels has never been reported. There could, however, be an advantage to the blue content in the LEDs. Because the blue content in LEDs has the potential to suppress melatonin, then by extension it may have the potential to make drivers more alert.
In order to design LED roadway lighting that minimizes any negative impacts on drivers, research is needed to understand the relationship between LED roadway lighting and driver sleep health and alertness.
The objectives of this research were to (1) evaluate the effects of LED roadway lighting on the sleep health and alertness of drivers, with attention to the illuminance, duration, and spectral power distribution (SPD) of the LED lighting; (2) compare these effects to those of (a) high-intensity discharge (HID) lighting and (b) the absence of roadway lighting; and (3) suggest methods to mitigate the effects, if any, of LED roadway lighting on sleep health and alertness. In this research, the term “sleep health” shall be construed to mean circadian disruption.
Publication of the project final report as NCHRP Research Report 968 is estimated in late Spring 2021. A preliminary, unedited version of the report is available here.