A mate of mine got a bridge strike on a B-road outside Lincoln about two years ago. The company TomTom sent him that way. The posted sign said 14'6". He'd been given a different trailer that morning — taller than the one he'd had the previous two weeks. Nobody told him. He'd never thought to check.
No one was hurt. The damage to the bridge parapet was real, though. And the damage to his record was realer still. Criminal Damage Act 1971. Network Rail involvement. A few thousand pounds and a very unhappy employer.
Bridge strikes in the UK run into the hundreds every year. Network Rail records them all. The same category of mistake shows up almost every time: driver relying on navigation that doesn't know the vehicle's actual height, driver not checking the posted clearance, driver not accounting for a trailer or body swap that day.
Why bridge signs are harder to read than they look
The UK has a mix of imperial and metric bridge signs. Older signs show clearance in feet and inches — 14'6", 15'0", 12'0". Newer signs are metric — 4.5m, 4.2m. Some bridges have both. Some have only one and it's the one you're not expecting.
The clearance shown is the lowest point. Not the average, not the centre, not the sides — the lowest point anywhere under that bridge. On a humped arch bridge, the lowest point is at the sides. On a flat-beam bridge, it's usually central. Either way, the number on the sign is the minimum clearance.
Here's the mistake I've seen drivers make — and I nearly made it myself once: treating the sign as a "safe for vehicles up to this height" marker and then assuming there's some margin above it. There isn't. If the sign says 14'6" and your vehicle is 14'5", you are theoretically within clearance. In practice, the vehicle might not be travelling perfectly level, the trailer roof might be bowed slightly from load, and "theoretically within clearance" can become a strike very quickly.
The safe rule: if the vehicle's height is within a foot of the posted clearance, find another route. That's not a legal requirement — there isn't a prescribed margin in the regulations — but it's the rule most experienced drivers apply. Under a foot of clearance, you're in territory where swaying, load shift, and road camber can turn fine into not fine in a second.
What your vehicle height actually is
This sounds obvious. It isn't.
The height on the vehicle registration certificate (V5C or the equivalent for a trailer) is the height when the vehicle is unladen. Put a load on, particularly a light bulky load, and that can change. A tautliner with a light load of packaging materials that's been soaked in rain — the roof distortion can add inches. A curtainsider with the straps not fully tensioned can bow.
Swap trailers, and the new trailer might be a different height from the old one. Couple to a rigid body on a different sub-frame height, and the overall combination height changes. If you're tramping — different unit, different trailer every few days — checking the height of that specific combination before you leave the yard is not paranoia. It's the thing that stops you from doing what my mate did outside Lincoln.
The marker lights at the top of the cab are a rough guide. The registered height on the trailer's certification plate is a better one. Best of all is actually knowing the vehicle you're driving before you commit to a route with restricted clearances on it.
Why the company satnav isn't your legal defence
Navigation systems — even ones marketed as HGV-specific — are only as good as the data they're working from. That data is updated periodically, not continuously. A bridge that was recently lowered for road surfacing below it, a temporary restriction on a diverted route, a clearance that was surveyed incorrectly when the database was compiled — none of those will show on your screen.
The legal position is this: you are responsible for the height of your vehicle and for not striking structures. The fact that a satnav directed you that way is not a defence to a criminal damage charge. Navigational systems don't carry criminal liability. You do.
That's worth thinking about before you follow the arrow.
HGV-specific navigation products like TruckMap or the Garmin dēzl series are better than consumer products at routing around restrictions. But "better" is not the same as "infallible." They'll route you away from known restrictions in their database. They won't know about the temporary restriction put up last Tuesday after a contractor damaged the clearance marker on an A-road in Lincolnshire.
The criminal law position
Striking a bridge and causing damage is almost certainly an offence under the Criminal Damage Act 1971. This applies in England and Wales; equivalent provisions exist in Scotland. The charge doesn't require deliberate intent — recklessness is sufficient. And "I followed the satnav" doesn't negate recklessness if a reasonable person in your position should have verified the clearance.
Network Rail prosecutes. The costs are two parts: the immediate prohibition and investigation, and then Network Rail's damage claim. That claim is often the larger part — not just repair to the bridge, but any costs from train delays, engineering works to assess structural integrity, and so on. I've heard of claims running to tens of thousands for what looked like minor structural contact. The driver doesn't always carry all of that personally — the operator's insurance is usually involved — but the operator's insurer remembers, and the OCRS record doesn't forget.
There's no fixed penalty tariff for bridge strikes the way there is for tachograph infringements. It goes through the criminal courts. That makes it more serious on your record than a PG9.
Route checking before a restricted-clearance area
Low bridges concentrate around certain areas: older city centres, agricultural country lanes, railway crossings on minor roads, industrial estate access routes. If you know you're going somewhere that might involve restricted routes — a town centre delivery, a rural industrial estate, anywhere off the dual carriageway network — check the route before you leave.
The National Highways bridge survey data is published. Ordnance Survey maps show railway crossings. A quick look at the route on a mapping tool that shows bridge heights can save a long reverse out of a lane. If you're going somewhere new and you're not sure, ring the site and ask. "Is there a height restriction on the route you want me to come in on?" is a sensible question. A good delivery site will tell you.
If you encounter a bridge with a posted clearance lower than your vehicle height — stop. Do not try to squeeze through. Do not rely on visual estimation. Reverse out and find an alternative. The delay of reversing is significantly shorter than the delay of a bridge strike investigation.
Abnormal loads — different rules entirely
If you're running abnormal loads under STGO (Special Types General Order) regulations — overheight, overwidth, or overweight combinations — the route survey is a formal requirement before the movement. You can't just plan your own route and hope for the best. STGO movements above a certain size require formal notification to the highway authorities, and for the largest movements, a police escort.
The height thresholds that trigger notification requirements under STGO have been stable for years. But the specifics — what notification is required for what height, and to whom — are worth checking directly with the DfT or a specialist haulier before you plan an abnormal movement. This isn't the sort of thing to work out on the day of the load.
What to do if you do hit
Stop. Don't drive on. Driving on after a bridge strike is a separate offence. Turn on your hazard lights, get out of traffic if you can do so safely, and call your depot. Network Rail has a dedicated number for reporting bridge strikes — 03457 11 41 41 — and they expect to be called. Calling them first, before anyone else reports it, is better than them finding out another way.
Document everything: photos of the bridge sign, your vehicle, any damage. Get the bridge reference number — it'll be on a plate attached to the structure. Don't move the vehicle until the police advise you can. The police will attend for any strike that involves structure damage.
Took me a while after my mate's incident to realise how avoidable all of it was. Twenty seconds checking the trailer height at the yard that morning would have changed the whole day. That's the thing about bridge strikes — they're almost always preventable, and they almost always feel obvious in hindsight.
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