THE EFFECTS OF OBSERVER AGE AND ENVIRONMENTAL GLARE ON NIGHT-TIME LEGIBILITY OF TRAFFIC SIGNS WERE INVESTIGATED IN TWO FIELD EXPERIMENTS WITH THE SUBJECTS DRIVING OR RIDING IN A CAR TOWARDS A SIGN. EXPERIMENT 1 SHOWED THAT EQUATING OLDER AND YOUNGER SUBJECTS IN TERMS OF THEIR LUMINANCE/HIGH CONTRAST VISUAL ACUITY RESULTED IN ELIMINATION OF ANY AGE EFFECTS ON LEGIBILITY. FURTHERMORE, THE PRESENCE OF A GLARE SOURCE WITH AN ILLUMINANCE OF 0.17 OR 0.017 LUX OFFSET 2 DEGREES FROM THE SIGN LEGEND IMPROVED LEGIBILITY DISTANCE SIGNIFICANTLY. THE RESULTS OF EXPERIMENT 2 INDICATED THAT A GLARE SOURCE WITH AN ILLUMINANCE OF 0.0098 LUX HAD NO EFFECT ON LEGIBILITY WHEN PRESENTED AT AN OFFSET ANGLE OF 1.5 DEGREES OR 0.6 DEGREES, BUT IT HAD A SIGNIFICANT DETRIMENTAL EFFECT AT AN OFFSET ANGLE OF 0.2 DEGREES. THE PRESENT FINDINGS SUGGEST THAT (1) THE USUALLY OBSERVED AGE-RELATED PERFORMANCE DECREMENT ON NIGHT-TIME LEGIBILITY TASKS IS THE RESULT OF VISUAL-ACUITY DEFICITS, AND NOT SHORTCOMINGS IN INFORMATION-PROCESSING ABILITY; (2) LEGIBILITY IS RELATIVELY UNAFFECTED BY GLARE, UNLESS THE GLARE ANGLE IS VERY SMALL OR GLARE LEVEL VERY HIGH; AND (3) GLARE SOURCES POSITIONED OUTSIDE OF THE FOVEA MIGHT IMPROVE NIGHT-TIME LEGIBILITY PERFORMANCE UNDER CERTAIN CONDITIONS. (Author/publisher).
Abstract