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 cycleway down underneath the M4, above the Duck Creek and the A'Becketts Creek. The path runs through the middle of the M4 cement columns which forms a scenic reminder, albeit suburban, of the functionality of the path. The path continues to follow the cement colonnade of the M4. On either side of the path are access points from Harris Park. Near the junction of Parramatta Road, Church Street, and Woodville Road, where the M$ passes over the junction, the cycleway provides various spur options: the north to Parramatta central business district via High, Wigram, or Railway Streets; and to the south