Braking and Cornering Effects with and without Anti-Lock Brakes 940723

The results of three inquiries of relevance to accident reconstruction are given. In the first the difference between anti-lock and locked-wheel braking on a dry surface is examined, with the finding that average decelerations with anti-lock are about 12% higher. In the second the effect of anti-lock operation on the curved yaw-mark method of speed calculation is explored; the finding is that the method is still valid, although it is possible that there is a greater tendency towards underestimation. The third inquiry is into the appearance and enhancement of tyre marks from anti-lock braking, where it is found that marks are infrequently made; they are more likely to be found on uneven surfaces, and while faintly visible marks can sometimes be seen more easily with polarised light, no way has been found of developing invisible or latent marks.