The Traffic Accident Reconstruction Origin -ARnews-

Re: Swerving to avoid a collision

Bruno Schmidt (SchmidtBF@aol.com)
Sun, 25 May 1997 18:49:03 -0400 (EDT)

A lateral acceleration value of 0.2 g in a swerve to avoid a collision appears too low. A value of 0.25 g to 0.30 g is more reasonable. In some testing done last year, Rusty Haight produced a value in that range. When he pushed things to the limit but still stayed in control, he was still close to the 0.3 g value. The resaon for this is that we cannot accelerate at a constant average value, but rather the lateral acceleration increases with time, then decreases with time, changing direction as the car returns to the same direction of travel but in an adjacent lane. That means, for an average acceleration of 0.3 g, the peak acceleration is in the neighborhood of 0.6 g, starting to approach the critical speed area. Since the swerve time varies with the square root of the lateral accelration, the time doesn't change very much as we change the acceleration from 0.25 g to 0.30 g, which is what we are usually interested in.

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