Paul L. Olson

Perception-response time to unexpected roadway hazards

Perception-response (PR) time, the time from the first sighting of an obstacle until the driver applies the brakes, is an important component of stopping sight distance. The purpose of this study was to measure the PR time of unalerted subjects to an obstacle in their lane encountered while cresting a hill. Data were obtained from 64 subjects, of whom 49 were young and 15 older. Measures were made of the time from first sighting of the obstacle until the accelerator was released, as well as accelerator-to-brake time. The results indicate a 95th percentile PR time of about 1.6 s for both age groups.

EFFECT OF DRIVER'S AGE ON NIGHTTIME LEGIBILITY OF HIGHWAY SIGNS.

A field investigation of the effect of drivers age on nighttime legibility of highway signs was performed. Subjects of two age groups (under 25 and over 61 years of age) participated. The results indicate that legibility distances for the older subjects were 65 to 77% of those for the younger subjects with equal high-luminance visual acuity. This finding implies that older drivers are likely to have less distance (and thus less time) in which to act on the information transmitted by highway signs. Consequently, it is argued that (I) legibility standards for highway signs should not be based exclusively on data obtained from young observers and (2) standard (high-luminance) acuity tests have questionable relevance to nighttime visual performance.

Comparison of headlamp visibility distance and stopping distance

This report compares experimentally-obtained headlamp visibility distances with stopping distances from 88 km/hr. The results indicate that low-beam headlamps are inadequate for safely revealing low-contrast objects at legal driving speeds.

RADAR-MEASURED REACTION TIMES OF UNALERTED DRIVERS TO BRAKE SIGNALS

This article concerns the responses of drivers to brake signals in actual traffic. The data were collected in a project investigating the potential benefits of high-mounted brake lights. The responses were obtained from unalerted drivers who at the time of the trial were following behind a test car and in front of a monitoring car. The test car (a compact or a full-size) was equipped on 69% of the trials with one or two supplemental brake lights, mounted just below the rear window or at roof level. A Doppler radar antenna was mounted at the center of the front bumper of the monitoring car. The radar monitored changes in the speed of the subjects vehicle and generated a trace on one track of an event-recorder. A telemetered input from the test car produced a deflection on the second track of the tape, corresponding to the start and end of the brake signal. The trials were run on two different routes, urban and suburban (speed: 32 to 40 km/hr and 56 to 72 km/hr, respectively; inter-car spacing: 1 to 2 car lengths and 3 to 5 car lengths, respectively). Only trials meeting all of the following criteria were included in the analysis: (a) The subjects vehicle did not appear to have braked or decelerated in response to vehicles ahead of or adjacent to the test car, to changes in roadway configuration or a traffic control device, or in preparation for turning off the roadway. (b) The roadway was generally flat. (c) The subjects vehicle was a car, van, or pickup truck. A total of 1,644 data points were collected. On 72% of the trials there was a discernible speed change within the 3 sec. following the signal onset, with a mean delay of 1.21 sec. and a standard deviation of .63 sec. By including no-responses and responses longer than 3 sec, the distribution of the speed-change delays under the present conditions can be characterized by a 72 percentile value of 3 sec.

Driver Responses to High-Mounted Brake Lights in Actual Traffic

This study evaluated brake responses of unsuspecting drivers to brake-signal presentations using a conventional brake- lamp system with and without supplemental high-mounted brake lamp(s). The signals were presented in actual traffic during the daytime at speeds of 48 to 72 kmlh. The main finding is that the signals given by the systems with one or two supplemental high-mounted brake lamps were more likely to produce a brake response by a following driver. On the other hand, the reaction times of the brake responses did not vary between the systems.

The Effect of Improvements in Motorcycle/Motorcyclist Conspicuity on Driver Behavior

A study was conducted to develop and evaluate various means of making motorcycles more conspicuous. More than 30 conspicuity treatments were developed, and the most promising ones were evaluated in day and night tests involving ordinary car drivers on public roads. The tests established which conspicuity treatments effectively deterred motorists from accepting short time gaps. Findings showed that daytime conspicuity of a motorcycle is significantly improved if (1) its normal low-beam headlamp is turned on or (2) its high-beam headlamp is turned on and is modulating in intensity three times per second or (3) the motorcyclist is wearing a high–visibility (fluorescent) vest and helmet cover. Nighttime conspicuity is significantly improved when the motorcycle uses additional running lights or the cyclist is wearing a retroreflective vest and helmet cover. Given that about three out of four motorcycle accidents occur in daytime, one major conclusion drawn from the study is that the most effective means of improving daytime conspicuity (considering performance, cost, and cyclist convenience) is to require motorcyclists to drive during the day with their low-beam headlamp turned on.

Glare From Automobile Rear-Vision Mirrors

Four studies were carried out to measure disability and discomfort glare from automotive rear-view mirrors. The results of the first three studies, which were concerned with disability effects, indicated that there are significant losses in forward visibility even at glare levels associated with low-beam headlamps. The last study measured comfort levels and showed that drivers rated even moderate glare levels uncomfortable, especially if they were exposed to them for a relatively long period of time. The implications of these findings for headlamp design are discussed.

Motorcycle Conspicuity Revisited

There is a widespread belief that motorcycles are more difficult to detect in traffic than are cars and trucks, which has led to much research designed to enhance motorcycle conspicuity. This paper examines the basic concept and finds that it lacks empirical support. Further, a number of other possible explanations could account for the differences one finds when comparing car-motorcycle and car-car collisions. Additional research is required to determine whether conspicuity is a special problem for motorcycles and the extent to which such a problem might contribute to crash involvement.

COMPUTERIZED VIDEO TASKS AS TRAINING TECHNIQUES FOR DRIVING-RELATED PERCEPTUAL DEFICITS OF PERSONS WITH BRAIN DAMAGE: A PILOT EVALUATION

This pilot study investigated the modifiability of perceptual deficits by training which consisted of performing microcomputer-generated video tasks. These commercially available remedial programs tapped a range of skills, such as right/left discrimination, color matching, visual scanning, judgment of line orientation, visual search, shape discrimination, visual memory, eye tracking, visuomotor coordination, and visual imagery. Four subjects with acquired brain damage were given 10 hours of training. Perceptual skills were assessed with a battery of seven paper-and-pencil tests administered both before and after the training. Following the training two subjects showed some improvement on several of the perceptual tests used, while two other subjects showed improvement on only a limited number of tests. Based on these results and on the performance changes on the video tasks themselves, a comprehensive evaluation of the potential benefits of this type of training on driving performance is recommended.

NIGHTTIME LEGIBILITY OF TRAFFIC SIGNS: CONDITIONS ELIMINATING THE EFFECTS OF DRIVER AGE AND DISABILITY GLARE

Abstract The effects of observer age and environmental glare on nighttime 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 low 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° 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° or 0.6°, but it had a significant detrimental effect at an offset angle of 0.2°. The present findings suggest that (1) the usually observed age-related performance decrement on nighttime 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 nighttime legibility performance under certain conditions.