Citation

Bullough J. IMSA J. 2003; 41(3): 51-53.

Copyright

(Copyright © 2003, International Municipal Signal Association)

DOI

unavailable

PMID

unavailable

Abstract

Standards for traffic signals in North America indicate that green signals need to have a luminous intensity that is 2.0 times greater that than of the red signal, while yellow signals need a luminous intensity that is 4.6 times greater than the red signal. In Europe and Japan, all three signal colors must have the same luminous intensity. North America has witnessed an increase in the use of light emitting diodes (LEDs) in traffic signals over incandescent bulbs, primarily due to LED lights requiring less energy and having a longer life. Currently, there are no standards-complying yellow LED traffic signals on the market. This article looks at issues such as the impact that luminous intensity might have on reaction times and the percentage of missed signals. It also emphasizes the need for standards-makers to consider what visual responses are required for each signal color and how a given luminous intensity provides the required visual response.