You are approaching a low railway bridge. A triangular warning sign shows a symbol of a vehicle hitting the underside of a bridge, with a rectangular plate beneath it stating 'headroom 3.7m (12'3")'. A separate red circular sign further along, right at the bridge itself, repeats a maximum height figure. What is the difference in purpose between the triangular sign with its plate and the red circular sign?
- There is no real difference; both are purely advisory and neither carries a maximum-height rule that must be obeyed
- The triangular sign only applies to double-decker buses, while the circular sign applies to all other vehicles
- The red circular sign is only used once the triangular warning sign has been removed for maintenance
- The triangular sign with its plate gives advance warning of a low bridge ahead so a driver has time to react, while the red circular sign at the bridge itself is the mandatory prohibition stating vehicles above that height must not proceed
Why D? And why not the others?
Correct answer: D. The triangular sign with its plate gives advance warning of a low bridge ahead so a driver has time to react, while the red circular sign at the bridge itself is the mandatory prohibition stating vehicles above that height must not proceed
The triangular sign belongs to the warning-sign family, a shape used to alert a driver in advance of a hazard, giving enough distance and time to slow down, choose a diversion, or check a vehicle's height against the plate figure before committing to the approach. The red circular sign positioned right at the bridge is a different sign type entirely: a maximum-height prohibition, legally banning any vehicle taller than the stated figure from proceeding under the bridge at all. Calling both signs purely advisory with no rule attached is wrong, since the circular sign is an enforceable prohibition rather than a suggestion. Restricting the triangular sign to double-decker buses is wrong because the warning applies to any vehicle tall enough to strike the bridge, not one specific vehicle class. Claiming the circular sign only appears once the triangular sign is removed is also incorrect; the two signs are complementary and are typically displayed together, one giving advance warning and the other marking the enforceable limit at the hazard itself.
Source: The Highway Code: Traffic signs — warning signs and signs giving orders (GOV.UK), low bridge and maximum height signs