FACTORS IN HIGHWAY SIGN VISIBILITY
SIMULATED SIGNS UNDER LABORATORY CONDITIONS WERE USED TO CONTROL MANY OF THE VARIABLES AFFECTING HIGHWAY SIGN VISIBILITY AND ATTENTION VALUE. BY CONTROLLING THESE VARIABLES, IT WAS POSSIBLE TO OBTAIN AN INDEX OF THE FACTORS MOST IMPORTANT IN DETERMINING WHICH SIGNS WERE "SEEN FIRST AND BEST." THE RECORDED SUBJECTIVE IMPRESSION OF THE SUBJECTS PROVED TO BE A BETTER INDEX THAN SEARCH AND RESPONSE-TIME METHODS. THESE INDOOR LABORATORY RESULTS WERE COMPARED WITH A NUMBER OF MATHEMATICAL MODELS. ONE BASED ON BRIGHTNESS RATIOS GAVE THE BEST FIT AND ANOTHER BASED ON PER CENT BRIGHTNESS CONTRAST THE NEXT BEST FIT TO THE EXPERIMENTAL RESULTS. THE LATTER WAS MORE EASILY APPLIED TO ESTIMATE VISIBILITY OF FULL SCALE TEST SIGNS. USING THE PERCENT CONTRAST EQUATION REASONABLY GOOD CALCULATED ESTIMATES WERE OBTAINED OF THE ACTUAL DISTANCES AT WHICH SIGNS WERE SEEN BY TWO GROUPS OF EXPERIMENTAL SUBJECTS UNDER DAY AND NIGHT CONDITIONS. THE NIGHT ESTIMATES WERE SOMEWHAT BETTER THAN THE DAY ESTIMATES PROBABLY AS A RESULT OF MORE VARIABILITY OF DAY VIEWING CONDITIONS. THE EXPERIMENTS INDICATED THAT SIGNS LOCATED OVER THE HIGHWAY WERE MORE LIKELY TO BE SEEN FIRST THAN THOSE TO EITHER SIDE. THE MOST EFFECTIVE FACTORS WERE BRIGHTNESS CONTRAST OF LETTERS-TO-SIGN AND SIGN-TO- BACKGROUND. INDICATED AS AN ADDED FACTOR IN SOME CASES WAS CHROMATIC OR HUE CONTRAST. TO MEASURE ALL OF THE FACTORS WHICH MAY HAVE SOME INTERRELATED INFLUENCE ON SIGN VISIBILITY A GREAT DEAL MORE WORK IS NEEDED. IN THE MEANTIME, HOWEVER, THE BRIGHTNESS RATIO AND PERCENT CONTRAST EQUATIONS MAY BE USED FOR ESTIMATION OF RELATIVE VISIBILITY OF GIVEN TYPES OF SIGN INSTALLATIONS. IN ADDITION, OF COURSE, ADEQUATE LEGIBILITY DISTANCES MUST BE PROVIDED. A METHOD IS SUGGESTED FOR MAKING THE NECESSARY ESTIMATES. ESTIMATES BASED ON BRIGHTNESS CONTRAST FACTORS SHOULD BE APPLIED WITH DUE CONSIDERATION OF THE WIDE RANGE OF BACKGROUNDS AGAINST WHICH HIGHWAY SIGNS ARE SEEN AS SHOWN IN OUR STUDY AND ALSO IN A STUDY BY HANSON AND WOLTMAN DIFFERENCES IN DIFFERENT SEASONS OF THE YEAR AS WELL AS FROM CHANGING VIEWPOINT OF THE DRIVER MUST BE CONSIDERED. /AUTHOR/
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Supplemental Notes:
- Vol39, No2, PP20-27, 9FIG, 12REF
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Authors:
- Forbes, T W
- Publication Date: 1969-9
Media Info
Subject/Index Terms
- TRT Terms: Brightness; Days; Laboratory tests; Legibility; Night; Overhead traffic signs; Seasons; Simulation; Traffic signs; Visibility
- Uncontrolled Terms: Seasonal variations
- Subject Areas: Highways; Operations and Traffic Management;
Filing Info
- Accession Number: 00225698
- Record Type: Publication
- Source Agency: Nat Safety Council Safety Res Info Serv
- Files: TRIS
- Created Date: Aug 26 1970 12:00AM