You are on a country road and see a triangular warning sign showing two black lines curving inward symmetrically from both edges toward the centre. Further along a different road, you see a similar sign where only one line curves inward, on the right-hand side, while the left line stays straight. What is the difference between what these two signs are telling you?
- The first sign warns of a bridge ahead with a weight limit; the second warns of a bridge ahead with a headroom restriction
- Both signs warn of exactly the same hazard, and the number of curving lines drawn simply depends on which sign-maker produced it, with no real difference for the driver
- The first warns that the road narrows from both sides at once, so vehicles from both directions lose width; the second warns that only the right-hand edge of the road narrows (or the left, if the symbol is reversed), so the road stays wider on the other side
- The first sign means the road is closed to any vehicle wider than 2 metres; the second means only vehicles taller than 3 metres are affected
Why C? And why not the others?
Correct answer: C. The first warns that the road narrows from both sides at once, so vehicles from both directions lose width; the second warns that only the right-hand edge of the road narrows (or the left, if the symbol is reversed), so the road stays wider on the other side
The 'road narrows on both sides' sign draws its two lines curving inward symmetrically because the carriageway loses width from both edges at once, meaning traffic travelling in either direction faces a narrower gap. The 'road narrows on right' sign (or on the left, if the symbol is reversed) only curves in one line, because only that edge of the road actually closes in, leaving the road wider along the untouched edge, so a driver should specifically watch for the disappearing edge on that one side rather than expecting the road to close in evenly. The option describing bridge weight and headroom restrictions misidentifies both symbols, since neither shows a bridge, an arch, or a height or weight figure. The option claiming the two versions are interchangeable and depend on the sign-maker ignores that the number and position of curving lines is a deliberately standardised difference conveying real, different information about which edge or edges of the road are affected. The option inventing specific width and height closures fabricates numerical restrictions that a plain road-narrows warning sign, which carries no figures at all, does not state.
Source: DfT Know Your Traffic Signs — Warning signs: Road narrows on both sides / Road narrows on right (GOV.UK)