The magnitude of the problem of driving-and seeing-safely at night is emphasized by the fact that death rates under nighttime conditions are substantially more than similar daytime rates. In urban areas, night death rates are almost three times day rates, while in rural areas, such night rates exceed day rates by two and a half times. Obviously, the special hazards of nighttime driving need extensive research, and application of such research where appropriate. The Committee on Night Visibility of the Highway Research Board for two decades has been focusing its attention on the research aspects of nighttime driving. Particular research findings as portrayed by recent papers are presented in this Record. 1: Burg, A.: Vision and driving; a summary of research findings, p. 1-12, 9 ref. To provide driver licensing administrators with heretofore unavailable information on which to establish effective vision-screening procedures for driver license applicants, a number of visual performance, personal, and driving habit characteristics of some 17,500 volunteer california driver license applicants were compared with their 3-year driving records (accidents and convictions). The vision tests included those for dynamic visual acuity, static visual acuity, field of vision, lateral phoria, low-illumination vision, glare recovery, and sighting dominance. Of these, dynamic visual acuity was most closely and consistently correlated with driving record, followed by static acuity, field of vision, and glare recovery. All relationships were in the 'expected' direction, i.e., poor vision was associated with poor record. As expected, among all variables studied, age sex, and average annual mileage play the largest role in influencing driving record. Accident and conviction frequencies increase with increasing mileage, are lower for females than for males, and are highest for the young age groups. Accident and conviction rates per 100,000 vehicle-miles decrease slightly with increasing mileage, are approximately the same for both sexes, and are highest for young drivers, followed by older drivers, with middle-age drivers having the lowest rates. The report gives recommendations for additional research and suggests practical applications of the present findings. 2: Hazlett, L.E. & Allen, M.J.: The ability to see a pedestrian at night: effects of clothing, reflectorization, and driver intoxication, p. 13-22 [Also published as: American Journal of Optometry and Archives of American Academy of Optometry, Vol. 45 (1968), No. 4 (April), p. 246-258, 18 ref.] In the United States, pedestrian deaths account for nearly 20 percent of all traffic fatalities. During darkness the pedestrian's risk is increased, and is further increased if a pedestrian is wearing dark clothing or must travel on a roadway concurrently with a driver who has been drinking. In the laboratory phase of this study it was found that at low levels of illumination an individual's sensitivity to contrast decreases as his blood alcohol level increases. In the road test phase, visibility distances were found to be unacceptably short for "dummy" pedestrians covered with black or grey fabric.' Dummies covered with white fabric were safely visible for a driver travelling at speeds up to 50 mph; however, only reflectorized dummies were safely visible above that speed. As blood alcohol levels of the observers increased, the visibility distance decreased for each of the simulated pedestrian conditions. 3: King, E.L. & Finch, D.M.: A laboratory method for obtaining pavement reflectance data, p. 23-33, 6 ref. Illuminating engineers have long known the importance of pavement luminance in roadway designs. It is also widely known that pavement luminance depends on the relative positions of the observer and the light source as well as the directional reflectance characteristics of the pavement surface. However, at present there is little information available that will permit the calculation of pavement luminance from an illumination specification. This paper describes the instrumentation and procedures associated with a laboratory method for determining the directional reflectance characteristics of pavement surfaces. In addition, data collected for one traffic-worn asphalt pavement surface are presented. 4: Rowan, N.J. & Ned. E. Walton: Optimizaton of roadway lighting systems, p. 34-47, 4 ref. The purpose of this study was to determine the optimum height and spacing of luminaries in lighting systems for access-controlled facilities. Considerations in determining the optimum geometric configuration were (a) obtaining a more functional system; (b) reducing glare; (c) reducing the overall cost of installation, operation, and maintenance, and (d) reducing the number of poles to reduce fixed-object hazards. 5: Forbes, T.W., Fry, J.P., Joyce, R.F. Pain: Letter and sign contrast, brightness, and size effects on visibility, p. 48-54, 3 ref. Experimental results are presented on sign size and brightness and letter-to-sign brightness ratio. This series of experiments was conducted to measure: (1) the effects of sign size, brightness, and letter-to-sign brightness ratio, and (2) the effects of competing signs on highway sign visibility. A typical highway scene for day or night conditions was projected continuously on the screen in front of the subject. From time to time under automatic control, keyed by its own responses to an auxiliary task, four simulated interstate green highway signs were flashed on the screen superposed on the previous highway scene. It was determined that the expected advantage for the largest of four signs was found consistently when the simulated green signs were seen against either day-snow or the night background. It was determined that an advantage for visibility was enhanced by a combination of: (1) greater sign brightness, (2) greater relative sign size, (3) contrast of sign against background, and (4) letter-to-sign brightness. Findings suggest that silhouette seeing is of importance for visibility or attention value where signs are seen against a bright background. Optimum combinations of these variables must be found to obtain best attention value and best legibility. 6: Forbes, T.W., Pain, R.F. Joyce, R.P. & Fry, J.P.: Color and brightness factors in simulated and full-scale traffic sign visibility, p. 55-65, 9 ref. A traffic sign requirements study was conducted on factors affecting ability and attention value. Outdoor observations were made by subjects riding over a standardized course. Mathematical models based on known visual and logical relationships were tested against each set of laboratory results. It was determined that average visibility and attention value of highway signs can be estimated from characteristics of legend, sign and environmental background. Relative brightness and contrast of sign-to- background and of legend-to-sign are of primary importance for visibility and the attention value. In visibility effects from colors, relative brightness is of most importance, but hue contrast enhances the brightness effects in some cases. For best visibility, a sign should be darker against a bright day background but brighter against a dark day or night background. A formula for estimating visibility effects is suggested on an approximate basis and within limits.
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