🚨 Emergency? Call 999 · Motorway breakdown? 0300 123 5000
Search
LIVE
Loading incidents...

Start typing to search

Find traffic updates, service providers, tools & more

📢 Seen an incident on this road? Report it in 30 seconds Report ›

At a glance

🕐 Last verified 18 Mar, 17:05

Loading the map…
StatusCleared
Severity (NH)Severe
RoadM4
DirectionWestbound
RegionEastern
CountyGreater London Authority
Category (NH)Accident
ReportedWed 18 Mar, 15:58
Cleared17:05
Lasted1h 6m
Road typeMotorway
Speed limit70 mph (variable)
Weather☀️ Clear sky
ReferenceREF-24534920
Views155

Times are UK time.

What National Highways say

M4 westbound between J4 and J4B | Westbound | Accident

Location : The M4 westbound between junctions J4 and J4B . Lane Closures : The hard shoulder, lanes 1, 2 and 3 are closed. Reason : Road traffic collision. Status : Currently Active. Time To Clear : The event is expected to clear between 16:45 and 17:00 on 18 March 2026. Return To Normal : Normal traffic conditions are expected between 16:45 and 17:00 on 18 March 2026. Delay : There are currently delays of 10 minutes against expected traffic. Lanes Closed : There are three of five lanes closed.

The official National Highways record of this incident, kept here after the road reopens.

Were you on the M4?

Enter when you were travelling to see if this incident was active at the time.

📡

Live Incident Timeline

1 update captured · Cleared

PREMIUM
M4 ✓ CLEARED

📋 Your Premium Report includes 1 timestamped update:

✓ Full timestamped update timeline
✓ Green-highlighted changes each update
✓ All 1 affected segments tracked
✓ Expected clear time per segment
✓ Weather & road surface at incident
✓ Emergency services confirmed
✓ Insurance claim checklist
✓ 3 ready-to-use template letters

A police collision report costs £215+ and takes 6–8 months. This report is available within minutes.

🚗 Were you caught in this incident?

Leave your email and we'll notify you when this incident is cleared and the full report is ready — useful for insurance or work.

We won't spam you. You'll get one email when this incident clears so you can grab the full report. This is an independent evidence report from official National Highways / TfL data — not a police report.

Also on the M4 today

M4 - Incident2h ago M4 - Incident7h ago M4 - Incident7h ago M4 - Incident8h ago M4 - Incident14h ago

Recent M4 incidents

182 incidents and roadworks logged on the M4 in the last 30 days, 56 of them serious or severe. Times are UK time.

M4 | Berkshire | Carriageway Closure | DelaysWed 9 Sep, 21:42 M4 | Berkshire | Carriageway Closure | Long Delays 30 minutesWed 9 Sep, 21:42 M4 | Greater London | Carriageway ClosureWed 9 Sep, 01:27 M4 | Gloucestershire | Road Closure | Expect DelaysWed 2 Sep, 22:45 M4 | Wiltshire | Carriageway Closure | Expect DelaysSat 15 Aug, 02:59 M4 | Wiltshire | Carriageway Closure | Expect DelaysThu 6 Aug, 09:35
Every M4 incident

Common questions

Is the M4 closed?

Not because of this crash. It cleared at 17:05 UK time on Wed 18 Mar. See the M4 right now.

What happened on the M4 on 18 Mar 2026?

Crash on the M4 westbound J4 to J4B in Greater London Authority, reported at 15:58 UK time on Wed 18 Mar. Cleared at 17:05.

How long did it last?

1h 6m, from 15:58 UK time on Wed 18 Mar.

Where can I see everything else on the M4?

The M4 live page shows what is happening now, and the M4 archive has every incident on record.

Share

WhatsApp Facebook X Telegram

Get M4 alerts

Free email alerts when something happens on the M4.

Early Warning · 7 days free

Know before you set off

Early Warning sends crashes, closures and long delays on your roads straight to your phone, plus email and Telegram.

Start my 7-day free trial

7 days free, then from £2.99 a month. Renews monthly until you cancel. Cancel within the 7 days and you won’t be charged.

Seen something on the road?Tell us once you've stopped somewhere safe. It takes a few taps and helps everyone heading that way.Report it

UK Traffic Updates is not a law firm and does not provide legal advice. We sell incident data and evidence reports only. We do not refer you to a solicitor, and we do not pass your details to anyone.

© 2026 UK Traffic Updates. Powered by National Highways’ Transport Data Feeds.

📄 Get Report