M4 motorway not signed, European route E30 includes most of the M4. The M4 has two sections of smart motorway. The one between junctions 19 (M32) and 20 (M5) north of Bristol has variable speed limits and a part-time hard-shoulder. Completion was in summer 2014. The section between junctions 24 and 29 in Newport has variable speed limits. In 2010 it was announced that a smart motorway would be constructed between junctions 3 and 12, with work starting in Autumn 2018. This will be the longest smart motorway scheme in the United Kingdom, with a length of 51km (32 miles). Work is
M4 Thames Bridge M4 Thames Bridge The M4 Thames Bridge Maidenhead is a motorway bridge between Dorney Reach, Buckinghamshire and Bray near Maidenhead, Berkshire in England built in the 1960s. The bridge carries the M4 Motorway across the River Thames, on the reach above Boveney Lock, and about 500 yards short of Bray Lock. It is one of three bridges carrying motorway traffic across the Thames, the others being the M25 Runnymede Bridge (just below Bell Weir Lock) and the M3 Chertsey Bridge. There is also a pedestrian walkway on either side of the bridge, which allows people to access Bray Village from