Lighting & visibility

Cracked mirror or dead lamp — drive it or park it?

Some are advisories you fix at the depot. Some stop you driving there and then. The difference usually comes down to two questions.

Ask yourself: can I still give a safe, legal signal or a proper view? and am I driving in the dark or poor visibility? A hairline-cracked mirror that still shows a clear view is usually fine to fix later; a missing or shattered mirror, or lighting you actually need right now, is a FIX IT FIRST — and a total loss of a required signal, like both brake lights, is a PARK IT.

The common ones, and what they are

Fault	Verdict	Why
Hairline-cracked mirror that still gives a clear, undistorted view	USUALLY OK	Record it and replace it — but the view is what the law cares about.
Required mirror missing, shattered, or so damaged the view is lost	FIX IT FIRST	Fix before a route with cyclists and pedestrians. Typically a £50–£100 penalty.
One headlamp out — and you're driving in the dark	FIX IT FIRST	Fixed penalty around £100; a delayed prohibition is possible.
One brake (stop) lamp of two not working	FIX IT FIRST	Rectify before further use — you're down to one warning to the vehicle behind.
Both brake (stop) lamps not working	PARK IT	No braking signal at all — prohibition, and rightly so.
Side/marker lamp out in daylight, good visibility	USUALLY ADVISORY	Fix at the depot — but don't let it wait past dusk.
ABS / EBS warning lamp stays on	FIX IT FIRST	A braking-system warning — a delayed prohibition is common.

Why "are you in the dark?" matters so much

A lot of lighting faults change category the moment the light fades. A single dead headlamp in bright daylight is a defect to log and fix; the same lamp at night, in rain, on an unlit road, is a genuine danger and far more likely to earn a prohibition. If a fault affects a light you're actually relying on now, treat it as fix-first, not fix-later.

The honest test for a cracked mirror

The mirror rule is about the view, not the crack. If a chip or hairline crack doesn't distort or obscure what you need to see, you're generally legal — record it and get it replaced. If the mirror is shattered, missing, or the crack breaks up the image so you can't properly see down the side of the vehicle, don't set off, especially where vulnerable road users will be.

Not sure how a fault is categorised?

Pick the vehicle, the area and the defect, and the free HGV Defect Checker gives you the drive-it / fix-it / park-it call and the likely penalty — straight from DVSA's categorisation.

Open the free checker → More guides

Based on DVSA's Categorisation of Vehicle Defects (examiners' handbook) and related enforcement guidance, current at July 2026.

Guidance only — not legal advice. Penalties vary with the circumstances, and at the roadside the call is the examiner's on the day. Roadworthy is an independent tool provider and is not affiliated with, or endorsed by, DVSA.