Assessment of Road Factors in Vehicle Performance during Exploitation

Vehicle practices sometimes require rapid assessment of the road gradient. The most common means to this is a satellite navigator with a barometric altimeter (BA). However, this is not always possible due to local or weather conditions. For such cases, the method of points of equal velocity (PEV) was proposed to measure parameters of the car forward movement and then of reverse movement through the same point and at the same speed and calculate the necessary road/car parameters. Driving through the same point in opposite directions at the same speed eliminates the unknown grade and rolling resistance, after which the system of equations is solved with a minimum of assumptions. Detailed recommendations given on measurements with the global positioning system (GPS)/Global Navigation Satellite System (GLONASS) navigator with BA and processing of results based on the author’s practical experience and because of their absence in the manuals. The error of the gradient values obtained after the required number of runs is less than ±0.001. The theory of the PEV method detailed recommendations for measuring and processing the results are given. Results of gradient determining do not depend much on the wind (oscillations from the average to 1%) and on the correctness of the vehicle C_d assessment (oscillations to 2%). The longitudinal profiles obtained by both methods are compared. The difference of gradients by the PEV method with the one by BA method is about 1 ppm on a smooth road and about 2 ppm on a steeper road with local pavement damage. Analysis and experiments have shown that in simple tasks it is possible to use the PEV method with an imported track from less accurate measuring instruments (5 decimal places) and to use old video records of display indications.