"Jack-knife" crashes

Press, Volume CXIV, Issue 33513, 19 April 1974, Page 5

"Jack-knife" crashes

Faced with evidence in "horrific detail” that articulated trucks, jackknifed across all three lanes of a motorway, can cause disastrous crashes, the British "run around metaphorically wringing our hands and mouthing cliches about 'motorway madness” instead of doing something positive about it. the “Daily Telegraph” has said.

According to the news-

paper’s motoring writer, John Langley. the authorities should insist that all articulated trucks he fitted with anti-lock braking equipment, which Would prevent jack-knifing. Such systems are not prohibitively expensive, he says: £lOO to £2OO on an £BOOO vehicle as original equipment. As it is. only a few British firms bother to fit antilock brakes. The success of an antilock system on trucks was reported on in detail four years ago by the British Road Research Laboratory. The laboratory’s tests with the latest Dunlop Maxaret system of the time showed that the system stopped jack-knifing completely.

Further tests with other systems and a variety of vehicles have been made since, and the results are likely to be published soon. About 60 per cent of the trucks on Britain’s motorways are articulated, and they are causing, and being involved in. a steadily rising number of serious motorway crashes.

If the rear wheel of a truck tractor unit locks under braking, the tractor unit starts to spin—and the trailer makes control almost impossible.

Anti-locKing systems prevent wheel-locking by relieving braking momentarily when the electronic sensor detects that the wheels are about to lock, then increases the braking effort again when it detects that the skid has been avoided. In this way. it allows the driver to make the maximum possible use of his brakes in adverse conditions without losing control. The adoption of the antilock systems is considerably more simple on trucks than on cars because the commercial vehicles already have fully-powered braking systems. ’ Jack-knifing of articulated trucks is not a problem in New Zealand, because the Ministry of Transport here insists 'on braking systems which give full instantaneous braking on both

tractor and trailer wheels of articulated rigs. Before this requirement was introduced, jack-knifing was a problem. The braking of articulated trucks in this country is said to be well ahead of British standards.