Getting Rollover Drag Factors Right

September 12, 2011 by · Leave a Comment
Filed under: Crash Reconstruction 

A comparison was conducted of numerous historical studies by reexamination of the original works, analysis of their data, and centralized compilation and analysis of their results. In total 81 dolly rollover crash tests, 24 naturally occurring rollover crash tests, and 102 reconstructed rollovers were identified.  Of the 24 naturally occurring tests 18 were steer induced rollover tests.

The range of drag factors for all examined dolly rollovers was 0.38 g to 0.50 g with the upper and lower 15 percent statistically trimmed.  The average drag factor for dolly rollovers was 0.44 g (Standard Deviation = 0.064) with a reported minimum of 0.31 g and a reported maximum of 0.61 g.   The range of drag factors for the set of naturally occurring rollovers was 0.39 g to 0.50 g with the upper and lower 15 percent statistically trimmed. The average drag factor for naturally occurring rollovers was 0.44 g (Standard Deviation = 0.063) with a reported minimum of 0.33 g and a reported maximum of 0.57 g.

Reevaluation of roll phase analysis published in two papers reporting results of rollover tests on an actual highway (Asay, 2009 and 2010) found lowered average roll phase drag factors as shown in table 1.  The average roll phase drag factor published in the papers was 0.53 g (min = 0.39, max = 0.74) and the average reevaluated drag factor was 0.45 g (min = 0.36, max = 0.52).  Reevaluation was performed from data published in the papers. A final analysis should be conducted using the actual test data.

Published results of reconstruction derived roll phase drag factors (Hight, 1972) between 0.40 g and 0.65 g was confirmed as the range representing the middle 60% of pre-1972 reconstructed rollover crashes on flat ground, figure 3. The reconstructed drag factors were in a range of 0.04 g to 1.20 g for all 102 plotted results, including downhill rollovers and rollovers with vertical drops.  For rollovers on flat ground the reconstructed range was 0.21 g to 0.83 g.