Ok this has probably been discussed here b4, sorry for asking again.
What is the bear minimum clearance you would conisder to be ok ■■?
I’ll tell you my delema after ive had some answeres & then we’ll see if I was right to take the diversion or not.
well, to be on the safe side I usually allow 1 inch 
Denis F:
well, to be on the safe side I usually allow 1 inch
Over or under? 
As long as the vehicle is no more than the height dispalyed on the sign then I will continue. Remember the height on the sign is the maximum height of a vehicle that is allowed to proceed and not the actual height of the bridge. So if the sign says 13’ 6" and the vehicle is 13’ 6" then I see no reason to divert.** The bridge will be higher than the height displayed on the sign so a clearance allowance has already been taken into consideration.
** This is dependent on knowing the exact height of the vehicle and not just a guess based on what it says on the headboard or what the last driver left the height indicator at.
Coffeeholic:
Remember the height on the sign is the maximum height of a vehicle that is allowed to proceed and not the actual height of the bridge.
Depends if it is signposted on a triangular sign or a round one.
As an aside, I’ve got under a bridge signposted at 11’ 3" with a 13’ 1" trailer before without touching it.
Harry Monk:
Coffeeholic:
Remember the height on the sign is the maximum height of a vehicle that is allowed to proceed and not the actual height of the bridge.Depends if it is signposted on a triangular sign or a round one.
Either or. A triangular sign would be giving warning of the maximum vehicle height and a round one would be prohibiting vehicles over the height indicated from passing the sign. So as long as you are equal to or less than the height indicated on the sign you can pass and you will be lower than the obstruction.
I agree with Coffeeholic baed on the fact that I am confident in knowing the correct height of my vehicle. Hence the Tape Measure in my bag
If it says 13 ft 3 then I am taking my 13 ft 3 under it. I may back off the power slightly if the road surface is bad to allow for a little bounce 
Harry Monk:
Denis F:
well, to be on the safe side I usually allow 1 inchOver or under?
generally under, but I have taken a 14’ high lorry under a bridge marked 13’9" before
( it was a bridge I knew well, and is marked cautiously )
cheers guys.
Last week had to under a 13:9 bridge now normally the motors are 13:6 with the old trailers. after doing my calculations 9:4 marked on the trailer & not knowing the exact 5th wheel height on a 6x2 volvo fm I based it on 1250 & worked that the height waxs about a little bit more than 13:6. But I wasnt sure if the water channel on the roof & the raised axle was taken into account, whichever there may only have been an inch or two at the most so I decided to take the diversion.
Today whilst leaving site I compared the two types of trailer & the new ones are a little bit taller & the one i looked at was marked based on a 1280 5th wheel giving a 13:6.7 runing height. again not taking into account axles.
Thinking about it now I probably could have made it but better safe than sorry.
to add the bridge is marked 13:9 with a red triangle on the A149 @ north walsham.
Denis F:
generally under, but I have taken a 14’ high lorry under a bridge marked 13’9" before
On the other hand, I have walloped a bridge signposted at 13’ 9" with a 13’ 1" TIR trailer in the UK.
I didn’t phone Railtrack to tell them. Well, why would you when all they are going to do is clobber you with a £2000 fine?
And as it happened five years ago I’m sure I would have heard about the Great T***** Rail Crash by now.
Why do Railtrack post notices telling you to phone them if you hit a bridge, then in the next paragraph tell you how much they are going to fine you when you do?
Hardly an incentive, is it?
Harry Monk if you do hit a bridge who has to pay the fine? Is it the driver or the company you work for?
Cheers Nige
If one of my driver’s hit a signposted bridge I certainly wouldnt pay the fine, that’s for sure.
As far as I am concerned it’s a driver’s responsability to know the height of their vehicle.
Harry Monk:
On the other hand, I have walloped a bridge signposted at 13’ 9" with a 13’ 1" TIR trailer in the UK.I didn’t phone Railtrack to tell them. Well, why would you when all they are going to do is clobber you with a £2000 fine?
Well, assuming you’re telling the truth, and that you didn’t try to go through an arched bridge without being in the middle of the road, why would they prosecute? A couple of photos, one showing the sign and another showing the actual height of the bridge (with a tape measure) should be ample defence.
You witnessed a truck hitting that bridge a few minutes ago.
No, you didn’t note the registration.
No, you are not willing to give them your details.
You are simply informing them of an incident which you think they will have an interest in.
I can see this problem from both sides, i was a class one driver for 5 years before i joined NETWORK RAIL (Railtrack ceased to exist in 2002). Bridge bashes are a major cause of delay to train operators. Everytime a bridge bash is reported all trains must be stopped on those lines affected until the bridge is examined, certain bridges are exempt from this, but the majority are not. An HGV striking a bridge has the capacity to dislodge the rails a significant amount, certainly enough to derail a train. Once the bridge has been examined the engineer has the option of restarting trains with a 5mph restriction, a 20mph restriction or if confident no structural damage had occured line speed may be authorised. This all takes time, and every minute a train is delayed a significant penalty is incurred by Network Rail so its only natural they want to punish offenders heavily to try and get the message across.
A previous poster makes a comment about the bridge on the A149 at North Walsham, this bridge is regularly struck by HGV’S despite the correct signs being in place, and a diversionary route signposted.
Sorry if this comes across a bit anorakish but i wanted to explain why the penalty for a bridge bash is so high. As for not reporting it you will be surprised at the amount of reports we get from witnesses who take the time to note vehicle registrations and a number of successful prosecutions have been secured in this manner, as well as a fine for the initial bridge bash there are also fines and points issued for failing to stop or report an accident.
offtherails obviously you know which bridge I am regarding as there are only two that i am aware of & the other bridge is lower 12 something, so do you know how accurate the signed height is on the bridge.
Though i have been laughed at by my fellow collegues for taking the diversion route I feel satisfied that i chose the right choice.
Evvo i take it you have your own trucks then?
I saw a truck which had clipped a bridge, today.
I was heading to Ayr on the A70 from the M74.
Just before you cross the A76 there is a bridge, marked as 4.2 m and the height in feet and inches too.
Just past it there was a red Simsons Bros’ trailer, pulled by a white with pale blue striped FH unit parked, with the front 6 inches of trailer roof peeled back. It looked like a very firm clip.
There’s another bridge, marked at 15 foot something, not far before it
robntl:
to add the bridge is marked 13:9 with a red triangle on the A149 @ north walsham.
I know the bridge well and from Cromer I don’t think it’s to well signposted judging by the amount of truck you see reversing from it.
There are three bridges round North Walsham all hinder large vehicles from getting onto the Industrial area. The lowest is the 13ft bridge on the Norwich road, by the station this stops you getting into the North Walsham bypass which is the easy route to the industrial area.
The next is the 13ft 9in Bridge on the Cromer road, this hinders traffic from Cromer direction getting to industrial estate.
then you have a 16ft bridge on the Aylsham road, sounds good, but it’s a small road almost impossible to get a car and truck past each other.
So basically the best way to get the North Walsham industrial estate in a large vehicle is to go to Holland and get a boat to Gt Yarmouth, of course you’d have to wait for them to build the outer harbour so there was a from Holland. 
and of course with a 4m trailer you’d have less problem with the bridges in North Walsham. 
I even know somebody who got a tilt under the 13ft bridge, but try that at your own risk.
robntl:
Thinking about it now I probably could have made it but better safe than sorry.
thats my opinion too. i diverted a 14’ bridge today with a 13’9 unit. if there is less than a 6 inch difference, i will find another route. i dont trust bridge heights to that degree of accuracy