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TRB's National Cooperative Highway Research Program (NCHRP) Report 828: Guidelines for Nighttime Visibility of Overhead Signs explores legibility distances for drivers in controlled conditions and the effects of sign luminance and visual complexity on the distance at which a driver can read overhead signs and street signs. While the Manual on Uniform Traffic Control Devices (MUTCD) provides minimum retroreflectivity standards for overhead signs, there are few guidelines that agencies can reference to decide how to provide sufficient nighttime performance of overhead signs in site-specific situations. The report presents proposed guidelines for nighttime overhead sign visibility, formatted as a potential replacement for the current Chapter 10, Roadway Sign Lighting, in the 2005 AASHTO Roadway Lighting Design Guide.


Suggested Citation

National Academies of Sciences, Engineering, and Medicine. 2016. Guidelines for Nighttime Visibility of Overhead Signs. Washington, DC: The National Academies Press.

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Publication Info

80 pages |  8.5 x 11 |  DOI:

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