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 required mirror missing or shattered so the view is lost, a headlamp out in the dark, or a total loss of a required signal, like both brake lights or an indicator, is a PARK IT. One brake light of two is a FIX IT FIRST.

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	PARK IT	No adequate view means an immediate prohibition. Graduated fixed penalty, usually band 1 (£50), non-endorsable unless the condition is dangerous.
One headlamp out, and you're driving in the dark	PARK IT	When headlamps are compulsory, a dead dipped beam is an immediate prohibition. Graduated fixed penalty, usually band 1 (£50). Lighting offences are non-endorsable, no points, unless the defect is bad enough to be charged as a dangerous condition, which carries 3 points.
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 before dusk; the same lamp at night, in rain, on an unlit road, is a genuine danger and an immediate prohibition. If a fault affects a light you're actually relying on now, treat it as a park-it, not a fix-later.

The defect checker with one dipped headlamp out in darkness: park it, do not drive, a dangerous defect and an immediate prohibition, with the driver and operator risk listed below. — The same call in the checker: one dipped headlamp out in darkness, with the driver and operator risk set out below it.

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 HGV Defect Checker, 3 free checks, gives you the drive-it / fix-it / park-it call and the likely penalty, straight from DVSA's categorisation.

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