Citation

Blackwell HR, Pritchard BS, Schwab RN. Highw. Res. Board bull. 1960; 255: 117-127.

Copyright

(Copyright © 1960, National Research Council (U.S.A.), Highway Research Board)

DOI

unavailable

PMID

unavailable

Abstract

Illumination data are presented for two roadway visual tasks: Seeing a mannequin and a black dog at various distances down the roadway with a variety of luminaire types and pavement surfaces. All measurements were made under an illuminative geometry that is representative of generally accepted practice in the country. Data suggest that: (1) 1.90 ft-candles of horizontal illumination are required for adequate visibility of the targets when they appear in the driving lane 200 ft ahead, (2) 5.7 ft-candles for the same targets to be adequately visible at the same distance when they appear in the curb lane, (3) 9 ft-candles if the targets must be seen 300 ft ahead, and (4) 48 ft-candles for 400-ft visibility in the driving lane. Moreover, these data reveal that there are visual tasks in night driving that are so difficult that they require interior levels of illumination.