Operational
Safety Training
for HGV Professionals

• 🧭Incorrect routing equipment — using a standard car satnav that does not account for vehicle height, weight, or width restrictions.
• 📏Unknown vehicle height — driver does not know the vehicle's OTH, particularly after loading when the load may exceed standard trailer height.
• ⏱️Delivery pressure — commercial time targets leading drivers to continue rather than divert when approaching a restriction.
• 📱Distraction at approach — phone use, radio, or conversation at the critical moment of approaching a bridge restriction.
• 🔄Route familiarity assumption — assuming a "known route" is safe without re-assessing after a diversion or load change.
• 🌙Reduced visibility — night driving or adverse weather reducing visibility of bridge height restriction signs.

The diagram above shows a vehicle whose Overall Travelling Height exceeds the bridge clearance. The driver must know their OTH and compare it to the restriction before approaching.

OTH is the height of the highest point of the entire vehicle and load combination. It is not the cab height. It is not the trailer height. It is the highest point of anything attached to or loaded onto the vehicle.

• 📏OTH card — the vehicle's maximum height must be recorded on an OTH card and be clearly visible to the driver at all times in the cab.
• 📦Loaded height — if any load item extends above the trailer roof or body, recalculate the OTH before moving. The OTH card figure alone is no longer valid.
• ❄️Refrigeration units — roof-mounted refrigeration units can add 300–600mm above the trailer roof. This must always be included in the OTH.
• 🔧Air suspension — if fitted, know the OTH in both loaded and unloaded states. An empty trailer on air suspension may be higher than a loaded one.

Use this tool to assess the working clearance margin for any bridge. A minimum of 0.3m is required to account for road camber, surface variation, and load movement.

Stop the vehicle in a safe position before approaching the bridge restriction. Hazard lights on. Engine can remain running. No other actions first — STOP is always first.

• ✅Pull over or stop before the restriction sign — not at it, not past it.
• ✅Activate hazard warning lights.
• ❌Do not answer the phone before stopping.
• ❌Do not attempt to assess clearance while the vehicle is moving.

Exit the cab and physically read the bridge restriction sign. Do not estimate from inside the cab. Do not rely on memory. Do not trust the satnav figure.

• ✅Read the bridge restriction sign directly. Note the figure.
• ✅Compare with your OTH card in the cab. Calculate: Bridge height − OTH = margin.
• ✅Check the road surface — is there visible camber, a dip, or humps on the approach?
• ✅If margin ≥ 0.3m AND road surface is level — you may proceed cautiously.
• ❌If margin < 0.3m, or if there is any uncertainty — do not proceed. Move to ESCALATE.

When clearance is insufficient or uncertain, escalate through the correct channels. Escalation is not failure — it is the professional response.

• 1️⃣Stop safely before the restriction sign. Hazard lights on.
• 2️⃣Exit the cab. Walk to the restriction sign and read it directly.
• 3️⃣Calculate: Bridge height − OTH = margin. Must be ≥ 0.3m.
• 4️⃣Assess the road surface on the approach — camber, dips, humps.
• 5️⃣If safe: proceed at walking pace, centrally, windows down.
• 6️⃣If uncertain: do not proceed. Call depot, divert, document.

Systemic failures:

• ❌No safety margin applied — OTH equal to restriction is not safe. The 0.3m margin must always be maintained.
• ❌Road camber not assessed — a 4% camber reduces nearside clearance by approximately 120–170mm.
• ❌Continued driving after contact — driving on after bridge contact is a criminal offence under the Railways Act 1993.

• ❌OTH card not updated — any change to vehicle configuration must trigger a review of the OTH card.
• ❌No pre-journey walkaround — a walkaround check would have identified the open vent.
• 🔑Rule: Your OTH card is only valid for the vehicle configuration it records. Any modification — open vents, additional equipment, raised aerials — requires a new OTH calculation.

• 01Know your OTH. Overall Travelling Height — highest point of vehicle AND load. Displayed in cab at all times.
• 02HGV routing equipment only. Programmed with current OTH, gross weight, and width. Car satnavs are not suitable for HGV routing.
• 030.3m minimum working margin. Bridge clearance minus OTH must be at least 0.3m on a level road before proceeding.
• 04Stop before the restriction sign. Never assess a bridge while the vehicle is moving.
• 05Exit the cab to verify. Read the restriction sign physically. Do not estimate from inside the cab.
• 06Road camber reduces effective clearance. A 4% camber can reduce nearside clearance by 120–170mm. Factor this into your assessment.
• 07Every route is a new assessment. Diversions, load changes, and equipment changes all invalidate previous route assessments.
• 08Escalate — do not gamble. When clearance is insufficient or uncertain: call depot, divert, document. Commercial pressure is not a legal defence.
• 09Railway bridge contact: 0800 833 557 first. Call Network Rail Emergency before anything else. This is a legal obligation and a life-safety action.
• 10Document every decision. A recorded diversion decision is evidence of professional competence. An undocumented bridge strike is evidence of the opposite.