MOT Windscreen Zones A and B at a glance
Zone A is the critical, central viewing band. It’s a 290 mm‑wide vertical strip, centred on the steering wheel, and only the area the wipers sweep counts. If your wipers don’t touch a part of the glass, MOT testers ignore damage there.
Zone B is the rest of the driver’s wiper‑swept area, outside that 290 mm band. Testers measure damage in millimetres: over 10 mm in Zone A fails; over 40 mm in Zone B fails. Use a ruler or your phone’s measure app. For official guidance, see the DVSA MOT manual (Visibility): gov.uk MOT inspection manual. For more detail, read will a damaged windscreen mean an MOT fail and our quick pre‑test guide, how to check if your windscreen needs repair or replacement before an MOT.
Zone A fail criteria (10 mm): what passes and what fails
- Chips, bulls-eyes or star breaks over 10 mm in Zone A = fail.
- Under 10 mm may pass, but treat as urgent and repair promptly.
- Cracks are measured by their longest line; over 10 mm in Zone A = fail.
- Stickers, dashcams, phone/sat nav mounts or toll tags obstructing Zone A can cause a fail—remove them before the test.
Small, clean chips often repair well if tackled early before dirt or moisture enters.
Zone B fail criteria (40 mm): what passes and what fails
- Chips and star breaks up to 40 mm can pass, but repairing prevents spreading.
- Any crack longer than 40 mm in Zone B = fail.
- Multiple smaller defects that collectively impair your view can also fail at the tester’s discretion.
Don’t leave “minor” damage to worsen—see how it spreads in how a windscreen chip turns into a crack.
Pass vs fail: simple visual scenarios you can copy
Pass example: a 5 mm chip near the passenger side, still in the swept area but outside Zone A. Likely pass with an advisory—book a repair to avoid cracking.
Fail example: a 12 mm star break in Zone A. Over the 10 mm limit, so it will fail. Depending on type and contamination, it may need replacement rather than repair.
Borderline example: a 30 mm bulls-eye in Zone B. Often repairable if clean and not running to the edge, but it needs inspection first. Keep the area clean and dry until we assess it.
This image was generated with AI and may not always represent the product or service exactly.
Repair or replace? Choosing the safe fix
- Repair is usually safe for a single, clean chip (typically under 25–30 mm, type‑dependent), away from the glass edge and not in Zone A. It should also be clear of sensors and HUD zones. Fresh, uncontaminated damage repairs better and looks neater.
- Replace the windscreen if you have long cracks, edge damage, multiple impacts, large bulls-eyes, contamination, or any failed Zone A defect.
After replacement, driver‑assist systems must be checked and reset. Learn how we calibrate locally in Beds, Bucks and Herts: ADAS calibration after windscreen replacement. Fleet Motorglass fits approved, E‑marked glass and bonds to OEM standards for safety and durability.
Mobile windscreen service across Beds, Bucks, and Herts
We come to you the same day in Milton Keynes, Aylesbury, Luton, St Albans, Bedford, Watford and nearby towns. Check our coverage: areas we cover. We handle repairs, replacements and ADAS calibration on site or at your workplace.
Expect fast response, clear pricing and help with insurance claims. Our ATA‑qualified technicians bring 25+ years’ experience and strong reviews. Cars, vans, fleets, EVs—routine or urgent, we keep you safe and legal before your MOT.
Before your MOT: quick self‑check and prep
- Find Zone A (290 mm wide, centred on the steering wheel) within the swept area and measure any damage.
- Act now if it’s over 10 mm in Zone A or over 40 mm in Zone B—see our guide: how to check before an MOT.
- Clean the glass inside and out, replace worn wipers, remove Zone A stickers, and ensure demisters work.
- Need help before your test? Book a mobile visit via contact.
This image was generated with AI and may not always represent the product or service exactly.
Window tinting and MOT visibility
Front glass must stay bright and legal. In the UK, the windscreen must let at least 75% of light through, and the front side windows 70%. Films that are too dark can fail the MOT or lead to a prohibition notice. Read the rules in window tinting rules and regulations.
Choose compliant films and keep them free of scratches and haze. Do not tint over camera or sensor areas, rain/light sensors or HUD zones. If you’re unsure, we’ll advise on safe, legal options that protect visibility and your MOT result.
Can I drive with a chip or crack? Safety first
Do not drive if a crack is spreading, a sharp line crosses Zone A, or anything blocks your view. Park safely and arrange a mobile inspection.
If you must move the car, keep speeds low, avoid potholes and don’t blast heaters or air‑con onto the glass. Cover a fresh chip with clear tape to keep out dirt and moisture, then book a prompt repair or replacement.
FAQs
How do I find Zone A on my windscreen?
Measure a 290 mm vertical band centred on the steering wheel within the wiper‑swept area. That strip is Zone A. Everything else in the driver’s sweep is Zone B.
Will every chip fail an MOT?
No. It depends on size and location. Over 10 mm in Zone A or over 40 mm in Zone B will fail. Smaller damage can pass but should be repaired quickly.
Is a chip in Zone A always a replacement?
Not always, but many Zone A defects are poor candidates for repair. We’ll assess size, type and contamination to confirm the safest fix.
Do I need ADAS calibration after replacement?
Yes. After a new windscreen, camera and radar systems must be recalibrated to restore AEB, lane assist and other features. A minor resin repair typically does not need calibration.
How long before I can drive after a repair or replacement?
Repairs usually take under an hour and you can drive soon after curing. Replacements have a safe drive‑away time based on adhesive—your technician will confirm.
Can you come to my home or workplace?
Yes. Our mobile service covers Beds, Bucks and Herts, including Milton Keynes, Aylesbury, Luton, St Albans, Bedford and Watford. We book 24/7 and work around your schedule.