Variability of Yaw Calculations from Field Testing 2009-01-0103
This paper discusses the variability of critical speed calculations from controlled field tests. A total of 29 tests were conducted at speeds of 80 to 95 km/h, using three different vehicles, three tire types, and variable braking levels. Results of the testing are provided. Analysis of the data revealed:
a chord length of 20 m measured from separation provided the most consistent results,
non-ABS braking affects the results of the critical speed formula, whereas ABS braking provides similar results as non-braked vehicles,
using 20 m chord measurements for the radius and the average braking coefficient of friction overestimated the measured speed at separation by 4.1% +/-6.3% (+/-1 standard deviation) for all non-braking and ABS braking tests,
using centre of gravity measurements along the curve for the radius and the average braking coefficient of friction underestimated the measured speed at separation by 2.0% +/-5.2% (+/-1 standard deviation) for all non-braking and ABS braking tests, and
there is a correlation between braking level and striation angle.