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davep3262 | 19:20 Sun 15th Jan 2006 | Motoring
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what is the minimum height of an unmarked bridge ?


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any bridge lower than 16 feet 6 inches must by law be marked either in feet and inches or metres.

if your are driving high sided vehicles every day then you may be better getting a bridge height map that tells you where all the low bridges are on most a class and b class roads. priced at �14.99

I agree about the 16 feet 6 inches. Bridge headrooms used to be indicated in multiples of 3 inches. In addition the requirement on the highway authorities is (or was) to build in a small safety margin of between 3 and 5 inches.

The height was measured from the road surface to the underside of the bridge at several obvious points, depending on the shape of the underside of the bridge and the shape of the road surface, and the lowest height measurement was used.

Then the safety margin was applied. So, for instance if the lowest headroom was measured as 16 feet 3 inches the figure displayed on the signs would be 16 feet 0 inches. If the measurement was 16 feet 2 inches, the figure stated on the warning signs would be 15 feet 9 inches.

But then, did you want to know this???
I drive under a 15ft 9ins with a 16ft trailer

I have been through 15''9' height restriction with 16'' trailer and by the time I got through I was nearly changing my under pants.

never again

I generally agree with 16ft 6in but I thought it had been metricated to 5 metres....near enough as makes no difference. [famous last words!]
Remember that on an arched bridge the height is shown at the pointed arrowheads, so with care it is possible for a higher vehicle to get through. I've seen a 14ft 6inch double-decker go under a bridge marked 13ft 9inches. Wouldn't recommend it though under any circumstances.

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