Reduced speed would increase A14 capacity

ONCE again we have one side of the A14 completely blocked by an accident involving three lorries and a van on Friday. Traffic was backed up on the A14 and right through Godmanchester for several hours.

It is strange how many accidents seem to involve heavy goods vehicles, and the average speed cameras have no effect on them whatsoever. Lorries should not exceed 50 mph on this type of road but the cameras are set to detect vehicles going more than 70 mph. Needless to say, most HGVs go at the maximum speed set by their speed limiter, which is nominally 56mph.

It is apparent that we are going to have to live with the A14 in its present form for a good many years to come. We should therefore be looking for solutions that can improve the traffic flow and reduce the number of accidents without spending enormous sums of money.

One fact that few people appreciate is that, when a stretch of road reaches its maximum capacity, the number of vehicles per hour that can pass through it can be increased by decreasing the maximum speed of the traffic. This comes about because the decrease in gap between vehicles needed to allow for reaction time and stopping distance more than compensates for the additional time that each vehicle takes to drive along the road.

I therefore suggest that the speed limit should be reduced to 50 mph, which will mean that the average speed cameras will be able to check that all vehicles, including the HGVs, drive within the limit. Since these cameras are capable of measuring the speed very accurately, it should not be necessary to allow a large margin for error, particularly since all vehicle speedometers are required, by law, to read on the high side.

The section of road that should be subject to the lower speed limit would be from Brampton Hut to Bar Hill, a distance of some 15 miles. In theory this should not slow down the lorries at all since 50 mph is their current limit.

Other vehicles that could travel at up to 70mph, when conditions allow, will take no more than an additional five minutes to cover this distance. This seems to be a small price to pay if the result is improved traffic flows at peak periods and a reduction in the number of accidents.

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