AT THE HEART OF THE ROAD TRANSPORT INDUSTRY.

Call our Sales Team on 0208 912 2120

a I recently saw an 8-ton vehicle on a

23th August 1968, Page 69
23th August 1968
Page 69
Page 69, 23th August 1968 — a I recently saw an 8-ton vehicle on a
Close
Noticed an error?
If you've noticed an error in this article please click here to report it so we can fix it.

Which of the following most accurately describes the problem?

motorway slow-lane fail to stop in time to avoid a pile-up ahead involving a number of vehicles. A similar vehicle that had pulled into the fast lane to avoid a collision stopped in a much shorter distance; in both cases all the wheels were locked and the speed was about the same—say 35/40 mph. To what factors would you attribute the difference in stopping distance?

AIn the first place, it would be impossible to make. a comparison between the actual stopping distances of the two vehicles based on observation. However, assuming the second vehicle stopped in a shorter distance, the most likely explanation is that the tyre treads were in better condition and/or that their inflation pressure was more nearly correct.

It might also be explained by the fact that the road surface in the fast-lane normally provides a somewhat higher coefficient of friction than the coefficient of the slow-lane surface. The continuous pounding of heavy vehicles can lead to deterioration of the slowlane surface in terms of friction coefficient before the surface is noticeably worn. This results from tyre rubber being scrubbed off on the road and from polishing of the road stones.

If the vehicles did not slew round to some extent it is doubtful whether in fact all the wheels were locked in either case. A nonlocking rear wheel can prevent slewing and can provide a better braking performance in the wet so long as the wheel approaches the locked condition.

The driver of the second vehicle may have -pumped" his brakes to simulate the effect of a non-locking brake. In this case some of the wheels may have skidded for some of the time: but the overall stopping distance would have

been reduced.

You do not say whether the vehicles were laden or unladen. Variations in loading can result in big differences in braking efficiency. A load-sensing valve fitted to the rear axle of a rigid truck or the tractive unit of an artic) can materially improve braking if the vehicle is unladen

Tags


comments powered by Disqus