30 March 2012 Last updated at 14:12 ET

Heavy vehicles ban on M4 near Heathrow due to cracks

Coaches, lorries and large vans have been banned from using a stretch of the M4 in west London after hairline cracks were discovered on a raised section.

The Highways Agency restricted vehicles weighing more than 17 tonnes from using the section near Heathrow on 24 March.

The restriction now covers vehicles more than 7.5 tonnes. It is a precautionary measure, the agency said.

Boston Manor Viaduct is being inspected after cracks were found in some of the welds in the steel beams.

Heavy vehicles are not allowed to use the westbound M4 between junctions 1 to 3, and the eastbound motorway between junctions 3 and 2.

Vehicles are being diverted on to the A312 and the A4.

A statement on the Highways Agency website said: "The restriction is a precautionary measure after a scheduled inspection on the Boston Manor viaduct, just west of junction 2, identified required maintenance work to the structure."

The agency said it could not say when the restrictions will be lifted but is confident the repairs will be carried out.