Abstract
Experiments were conducted to determine drivers and pedestrians sensitivity to speed and speed changes. Subjects were in the front passenger position instead of driving the test vehicle. A midsized car was the test vehicle and a closed track was used. Absolute judgments were estimates of speed in miles per hour, (mph). For relative judgments, subjects decided whether a second run of the test vehicle was "faster" or "slower" than a first run. In Experiment I both absolute and relative judgments were obtained in counterbalanced sessions. The same subjects were used as passengers and pedestrians. A 100 foot pedestrian-vehicle separation distance was used. When passenger and pedestrian data were combined the speed estimates in mph were accurate and consistent. Most estimates were in increments of 5 mph. Slow speeds (10-20 mph) were estimated most accurately with an increasing overestimation at higher speeds so the mean estimate for 49 mph was 55.64 mph. Standard deviations (SD) of speed estimates did not increase significantly as speed level increased. The estimates were linear over speeds and a Weber fraction of 0.18 was found to describe the combined data. The correlation of estimated to actual speed was 0.92. Passengers estimated lower speeds than pedestrians at slow speeds. However, by 34 mph both passengers and pedestrians were overestimating by the same amount. Day or night light conditions did not have an effect on speed estimates. Women estimated higher speeds in mph than men at all speed levels. A position by sex interaction suggest womens speed estimates were closer to male estimates as drivers than as pedestrians. Subjects over 35 years old estimated higher average speeds at all levels than subjects under 35. For relative judgments of speed, comparison runs of plus and minus 2 and 5 mph were conducted around standard speeds of 15, 30 and 45 mph. Comparison runs which were the same speed as the standard were also made. For relative judgments, speed differences of 5 mph were discriminated consistently at all three speed levels. Differences of 2 mph also could be discriminated, but the results required interpretation...
Bergman, Michael Harmon (1981). Passenger and pedestrian speed estimations. Doctoral dissertation, Texas A&M University. Texas A&M University. Libraries. Available electronically from
https : / /hdl .handle .net /1969 .1 /DISSERTATIONS -83383.