Had a situation the other day where the vehicle i was driving was 15ft 6inch high and a bridge on my route was 15 ft 9inch. Decided to go another way in the end.
Was I right taking another route or just being over caustious?
Just wondering what you would have done?
i would have changed my route,
better safe than sorry IMO.
If I’d measure the vehicle myself and knew the measurement was spot on I’d take it. If you hit the bridge then it wouldn’t have been your fault.
If it was a cab marker I’d not trust it until checked.
But if the deter wasn’t massive I’d possibly take it. After all if the bridge is marked incorrectly and you hit it, you are still going to get some serious grief over it.
I know a recent case of a colleague who approached a bridge where the bridge marker gave him 3" over his supposed trailer height.However,he was driving a 6 X 2 with the second axle raised,and in case some of you don’t know,that can tranfer to raise the ride height of the drive axle,which meant his normal trailer ride height was considerably higher.Result?One trailer with a sloping headboard!
I keep a tape measure in the locker and always check the hight of the trailer and alter the indicator. Its all to easy to get used to a certain hight if you use a trailer frequenttly and then get caught out.
High-Vis:
Had a situation the other day where the vehicle i was driving was 15ft 6inch high and a bridge on my route was 15 ft 9inch. Decided to go another way in the end.
Was I right taking another route or just being over caustious?
Just wondering what you would have done?
i always take the stated trailer height and add 6 inches. if the bridge is lower than that, i go round
I had to go through a local town the other week with a artic. Trailer was 14ft6 bridge I knew was 15ft9. Anyway my passenger at the time questioned if we could get under the bridge in Market Rasen town centre. I said yeah its 15ft something nay bother, he said are you sure and having already double checked I was so we carried on. But im now looking for the warings for the bridge. As you turn from Middle Rasen into Market Rasen you would expect a warning there at least. No sign nothing so pressed on regardless amazingly the first warning I saw for it was 50 yards before it smack bang in the town centre. Now I may of missed a sign but I was looking even more than normal so dont think so. What ammuses me is what the hell are you supposed to do once your there and cant get under its errrrr a long way to reverse and little room for turning.
If you knew for sure the height of your vehicle, you had measured it rather than going by any in cab indicators or headboard markings, then I see no reason to deviate as you had ample clearance.
I noticed you said the height of the bridge was 15’ 9" but remember the sign is not indicating the actual height of the bridge, it is indicating the maximum height of a vehicle able to pass under it. So, if the sign says 15’ 9" the bridge itself will be higher than that to allow 15’ 9" vehicles to clear it. The actual description of the maximum height sign as given in the Highway code is, “No Vehicles Over Height Shown” and to allow a vehicle of the height shown to pass beneath the bridge it will be higher than the height on the sign. That is why you hear drivers saying things like - “The bridge is 3.9 metres but I can get my 4.0 metre trailer under it.” 
Was in a situation a few weeks ago where the height indicator for the vehicle was 3.9m and the bridge was 4.1m.
Had raised the suspension up at the previous stop as the low ride height warning light had come on.
Wasn’t sure how this would affect the clearance so did a detour of 600 yards around bridge,better safe than sorry.
You got the truck back in one piece and didn’t hurt anybody or damage anything, so I reckon you made the right choice. I always approach bridges with a marginal clearance really slow and sometimes even stop. and get out and look.
Even if you have a few inches to spare, (stop laughing at the back 
) I reckon you should slow down to avoid the trailer bouncing about.
The closest I got was scraping the top of a tilt on a bridge, the alternative was to reverse blind onto a main road, so took the chance and got away with it.