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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.

The Mannesmann Kienzle UDS2165 Accident Data Recorder has been fitted to several vehicles in a fleet of cars in London as a trial of its effectiveness as an accident investigation tool. The characteristics of the device, which provides a record of driving for 30 seconds before and 15 seconds after an accident, are described together with the results from our trials. The advantages of such a device are considerable, in that it provides information which is either of greater accuracy than that obtained by traditional methods, or which is not otherwise available at all. This includes speed and acceleration, heading angle and the use of brakes, direction indicators and lights throughout the whole 45 second period.