The M4 motorway is 189.5 miles (305 km) long in the south of England. The M4 motorway runs from London (Chiswick) at it's eastern end  and runs directly west to Pont Abraham services in Llanelli in South Wales.

Primary destinations are Hounslow, Heathrow Airport, Slough, Maidenhead, Reading, Newbury, Swindon, Chippenham, Bristol, Newport, Cardiff, Bridgend, Port Talbot, Swansea, Llanelli.

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. 

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

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