00334171

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Considerable energy savings can be achieved by changing overhead-sign illumination from 125-W mercury-vapor (MV) to 70-W high-pressure-sodium (HPS) luminaires. Studies (which included measurements) were carried out to show the technical viability of such a change. The average illumination levels remained sufficiently high, and uniformity did not change significantly. The results were evaluated by comparison with various standards; they are discussed with respect to two aspects of visibility--attention value and legibility of messages. With regard to legibility, a new concept is introduced--the relative local gradient of illuminance or of luminance, i.e., the percentage of change in these values in any direction per unit of length. Since the extreme values of these gradients along distances of the order of the size of a letter interfere with legibility, it is suggested that uniformity standards be based on this concept rather than on the traditional ratios of maximum to minimum or average to minimum values. Luminance contrasts were investigated for various common color combinations of letters and background for both light sources. It was found that luminance contrasts generally increase when a change is made from MV to HPS luminaires. The change from MV to HPS luminaires in sign lighting does not decrease technical performance. (Author)

Publication of this paper sponsored by Committee on Visibility.

01411593

pp 17-20

1980

Transportation Research Record

0309031176

Print

References (8) ; Tables (4)

Attention value; Brightness; Illuminated traffic signs; Legibility; Lighting; Sodium vapor lamps; Visibility

Highways; Operations and Traffic Management; Safety and Human Factors; I73: Traffic Control; I83: Accidents and the Human Factor

TRIS, TRB

Oct 28 1981 12:00AM

• COUNTERMEASURES TO IMPROVE SAFETY AT MULTILANE RURAL INTERSECTIONS (ABRIDGMENT)
• EVALUATING THE SAFETY BENEFITS OF RAILROAD ADVANCE-WARNING SIGNS
• EVALUATION OF AN ALGORITHM FOR DETECTING URBAN FREEWAY INCIDENTS DURING LOW-VOLUME CONDITIONS
• INVESTIGATION OF THE EFFECT OF LOCATION OF FREEWAY TRAFFIC SENSORS ON INCIDENT DETECTION
• NIGHT VISIBILITY OF TRAINS AT RAILROAD-HIGHWAY GRADE CROSSINGS. ABRIDGMENT
• ON FORECASTING FREEWAY OCCUPANCIES AND VOLUMES (ABRIDGMENT)
• OPTIMUM LENGTH OF TWO-LANE TWO-WAY NO-PASSING TRAFFIC OPERATION IN CONSTRUCTION AND MAINTENANCE ZONES ON RURAL FOUR-LANE DIVIDED HIGHWAYS
• SELECTION AND EVALUATION OF OPTIMAL FREEWAY DESIGN BY COMPUTER SIMULATION
• TRANSVERSE PAVEMENT MARKINGS FOR SPEED CONTROL AND ACCIDENT REDUCTION (ABRIDGMENT)