M4 Motorway

The M4 Motorway

The M4 links London with Reading, Swindon, Bristol and South Wales. Our M4 website has been reporting M4 traffic news since 2011, for commuters around Heathrow and the Thames Valley as much as for longer journeys west.

Our M4 Website

Everything you need for the M4 is on m4traffic.co.uk, updated every five minutes, 24 hours a day, from official National Highways data. It includes:

• the latest M4 traffic news
• accidents and incidents
• roadworks
• what the overhead signs are saying
• the variable speed limits in force now
• a map of M4 junctions

It is one of a family of websites from UK Traffic News, each one given over to a single road so that the news you see is about the road you are actually driving.

Information About the M4 Motorway

How long is the M4 Motorway? The M4 motorway is 189.5 miles (305 km) long

Where is the M4 motorway? The M4 is in the South of England.

Where does the M4 go? The M4 motorway runs from London (Chiswick) at its eastern end and runs directly west to Pont Abraham services in Llanelli in South Wales.

What are the primary destinations on the M4? Primary destinations are Hounslow, Heathrow Airport, Slough, Maidenhead, Reading, Newbury, Swindon, Chippenham, Bristol, Newport, Cardiff, Bridgend, Port Talbot, Swansea, Llanelli.

When was the M4 built? The M4 was constructed between 1961 (Junctions 7 to 9) and 1996 (Junctions 21 to 23).

The M4 is a busy commuting motorway particularly from Newbury (Junction 13), Reading (Junction 12 West Reading, Junction 11 Central Reading and Junction 10 East Reading), Maidenhead (Junction 8/9), Slough (Junction 7 Slough and Windsor Junction 6 and east Slough) to the M25 (Junction 4B) and into London.

As the main link from London to South Wales it can get very busy on Bank Holidays and peak holiday periods.

Link to central London (Chiswick) in M4 inside the M25 ring can get extremely busy during rush hour.

Was the M4 the first motorway built in the UK? No. The first UK road to be built to motorway standard was the Preston Bypass which later became part of the M6. The first motorway was the M1.

The M4 in numbers

Traffic on the M4 as counted by the Department for Transport.

about 90,000

vehicles a day

on an average stretch of the M4. The busiest stretch carries about 156,000 a day.

1 in 14

vehicles is a lorry

and about 1 in 6 is a van, so a large share of M4 traffic is people at work.

Source: Department for Transport road traffic statistics, 2025. Averages across the whole road; rounded.

See also: M4 traffic reports · all the motorways we cover.