M4 J28 Improvement 10 April 2017
Modifications to the existing roundabout at M4 junction 28, which handles interchange movements between the M4 sliproads, the A48 and the A467. The roundabout will be modified to a teardrop shape, with closure of the part between the westernmost entrance and exit, and a new cut-through installed to enable traffic travelling eastbound on the A48 to pass through the middle of the junction. A new section of road will pass around the west side of the flyover carrying the eastbound A48 to replace the closed section of roundabout.
M4 J3-12 Managed Motorway 22 March 2017
Upgrade of the existing M4 between junctions 3 (Hayes) and 12 (Theale) to Smart Motorway, with the hard shoulder converted to an extra traffic lane for most of that length.
Unusually for a Smart Motorway scheme, bridge widening and replacement works will be carried out to provide extra space on parts of the motorway that presently carry three lanes with no hard shoulder. The M4 Slough and Maidenhead Bypass sections were subject to "rapid widening" in the 1970s which left the motorway with a discontinuous hard shoulder through bridges.
M4 Newport Relief Road 8 March 2017
Construction of a new dual three-lane motorway to the south of Newport, from junction 23 of the existing M4 to junction 29, in order to replace the existing motorway which suffers severe operational and congestion problems.
This solution has been chosen partly because widening the M4 and bringing it up to modern standards would be prohibitively difficult - in particular with regard to the Brynglas Tunnels and the twisting alignment.
M4 J19-20 and M5 J15-17 Managed Motorway 7 October 2014
Introduction of dynamic hard shoulder running (use of the hard shoulder as a fourth lane during busy periods) on a section of the M4 (J19-20) and M5 (J15-17) north of Bristol. The aim of the scheme is to increase the capacity of the existing road space, and thus reduce congestion.
M4 Variable Speed Limits Magor - Tredegar Park 17 June 2011
Upgrade of the central reservation to concrete step barrier, and the construction and implementation of a Variable Speed Limit scheme, between junction 23A (Magor) and Junction 28 (Tredegar Park). This will replace the current temporary 50mph speed limit on the M4 Newport Bypass.
M4 J11 Reading 8 January 2011
Reconstruction of M4 junction 11, the connection point for the A33 and large parts of Reading. The junction improvements will add a new gyratory system around the outside of the existing roundabout, with the current bridges used for a bus priority route through the middle of the new junction. It will facilitate park and ride facilities that are proposed close to the site.
M4 Widening J29-32 7 September 2010
On-line widening of the M4 between junctions 29 and 32 (the Cardiff bypass section) to dual-three lane motorway. The scheme was procured under an 'Early Contractor Involvement' contract. The Works are being administered under the NEC 2nd Edition Option C - an old version of the New Engineering Contract. The contractor carrying out the works will get a modest bonus for finishing on time and on budget but will be fined if they overspend.
M4 Toll Newport Bypass 15 July 2009
Construction of a new dual-three lane motorway standard bypass to the south of the city of Newport. The route has been planned for many years to relieve the existing M4 bypass, which runs through tunnels to the north of the city and cannot be widened. The plan has now finally been confirmed, as a privately financed toll road on the model of the M6 Toll.
It seems likely the new road will tie in to the existing M4 at or near to the existing junctions with the M48 and A48(M), in which case it seems likely that the existing Newport Bypass and A48(M) will be renumbered as M48.
M4 J13 Chieveley 26 October 2008
Upgrade of M4 junction 13, where the A34 currently crosses the route. The plans will divert the A34 to the west of the junction on three miles of new dual carriageway to pass under the M4 without a junction, with the present dual carriageway through the M4 junction becoming a connecting road merging with the A34 at each end of the new section.