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Abstract
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A simple decelerometer offers an inexpensive, convenient, and adaptable means of measuring pavement friction. To evaluate the accuracy of such measurements, a tapley decelerometer was included in a vehicle making locked-wheel stops.
RESULTS were compared to measurements of the same pavements obtained by the stopping-distance method and several towed trailers. Because the several machines obtained such large and consistent differences in measurements, it was not possible to make a precise evaluation of the accuracy of any one method. The decelerometer results appeared to be as valid as those obtained by the other more commonly used methods. It seems clear that the decelerometer can yield results which have at least a rough-and-ready accuracy. In terms of reliability and consistency of results it compares favorably with other methods. In the opinion of the authors, this simple and inexpensive device, if used with a minimum of care, can yield results of considerably greater accuracy than a number of much more complex devices already in use. However, transient changes in decelerometer readings, presumably a function of the suspension system of the american car used and/or the rate of brake application, cast some doubt on reliance on decelerometer readings for precise measurement. It is not clear whether the transient changes represent real changes in deceleration of the vehicle, or are an artifact of the instrument and the way it was used. If the transients are artifacts that can be overcome, such a decelerometer is a very promising method for measurement of pavement friction. If real transient changes in deceleration exist, there are important implications for relationships between friction measurements made by trailers and the skidding distances of vehicles. Further research is indicated on (1) the use of decelerometers, (2) the irregularities of the deceleration of skidding cars, and (3) the relations between friction measurements by the stopping-distance method and by towed trailers. |