Work widening the Thames motorway bridge between Dorney Reach and Bray will close the M4 between Slough and High Wycombe for a second weekend.

The bridge carries the M4 across the Thames on the reach above Boveney Lock about 500 yards short of Bray Lock.

Over two weekends it is being widened to fit an extra lane in each direction - all part of the plan to add extra capacity on the M4 between London and Reading.

The widening represents one of the most complicated challenges of the motorway upgrade.

The bridge carries the M4 motorway across the River Thames onto the reach above Boveney Lock, and about 500 yards short of Bray Lock.

Over two weekends huge steel beams to form the deck of the widened bridge will be lifted into place. The beams have been prefabricated into three sections, weighing nearly 300 tonnes, so they can be installed while keeping the time that the road need to be closed to a minimum.

While the work is being carried out the the M4 has to be closed in both directions between junction 6 (at Slough) and junction 8/9 (for High Wycombe) with diversions in place.

It happened last weekend and will happen again from 8pm this coming Friday until 6am on Monday, June 8.

The size of the beams and the cranes required to lift and position the beams will also involve stopping navigation on the River Thames between Boveney and Bray locks for a second weekend. The Environment Agency will issue a Harbour Master’s Notice for this stoppage.

To accommodate the new 4-lane smart motorway, the bridge requires an 8-metre extension on its north side. This will be in the same style as the existing structure and will be complete and open for use in 2021. The smart motorway upgrade is expected to be open for traffic in 2022.