Browse Publications Technical Papers 2009-01-0103
2009-04-20

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.

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