M4 improvement plans

Highways England came to see me to explain their plans to widen the M4 out to Junction 12 under their so called Smart Motorway project.

The aim is to provide a 33% increase in capacity by making a 3 lane a side highway into a 4 lane one. There need to be bridge works, new emergency reservations have to be constructed, a new central barrier installed, and new sensors and signs to regulate traffic flows and speeds.

Most of the work will take place at night. The motorway will be tackled in sections, starting in the west. Whilst works are underway on a section there will be 50mph narrower lane operation for traffic, with closures overnight when needed.

Works will start later this year, with completion of the whole motorway J 3 to J12 by March 2022

I stressed the importance of putting in the promised new noise barriers and noise reducing surfaces for the road.

I also stressed the need to keep the motorway flowing as freely as possible during the works, as this motorway is crucial to constituents travel plans and daily lives.



  1. Adam
    May 25, 2018

    A more efficient method:

    Use existing space.
    Remove the central barrier & use it as the emergency lane.
    Position slow traffic at centre; fast traffic wide apart.

    Lane 1: 20mph
    Lane 2: 40mph
    Lane 3: 40mph
    Lane 4: 60mph (old duplicated hard shoulder)

  2. alan jutson
    May 25, 2018

    Given this four lane project is going ahead without a safety hard shoulder, can I ask you to try and make sure that safety refuge zones are placed at rather more sensible closer intervals than the long distances (over a mile) apart that feature on the recently opened M3.

    Have seen a couple of breakdowns over the past months where the vehicles concerned could not make it to the safety areas, and are thus stuck in a live lane.

    Reply I did ask for just that, and for more noise barrier

    1. Adam
      May 25, 2018

      The solution for breakdown refuge is indicated in my 8.06am post above.

      If the central barrier is removed, its space can be used efficiently as a continuous lane for emergencies. Instead of having 2 wasteful, rarely-used hard shoulders, the facility is shared at the slow centre of the motorway.

      On many British roads, traffic from opposite directions shares the same road space at passing speeds of 60mph: risking impact at 120mph. The emergency lane at the centre of the slow centre motorway is for solely for stationary vehicles, & is cushioned by being between two 20mph slow lanes.

      Whereas on many of our roads 120mph collision can occur within the same lane (during overtaking), such impact on a slow centre motorway could occur only if a vehicle crossed EIGHT lanes in the process!

      The arrangement might at first seem difficult to envision, yet is simple & efficient. If you have a query I shall respond endeavouring to assist.

      1. alan jutson
        May 26, 2018


        Certainly sounds sensible not to have high closing speeds from opposite directions close together, but then you have the complications of slip roads with leaving and joining, and educating drivers that Motorways are completely different from any other roads in operation with regards to overtaking.

        So I would suggest your solution a step too far.

        1. Adam
          May 26, 2018

          The solution is simpler & more efficient, Alan, than your described perception of it suggests.

          There is no complication in entering or leaving the slow-centre motorway. As in existing systems, when vehicles cross the path of other traffic, flyovers or tunnels are used to prevent obstructive stops. Joining existing motorways often involves merging into the nearside lane with traffic approaching at 70mph. The new method is much safer.

          No added driver education would be involved, as overtaking on the slow-centre motorway is identical to existing motorways. You would drive just as on a one-way 4-lane road. The only difference would be an identical 4-lane road approaching from the opposite direction, with its fastest traffic 8 lanes apart, & an emergency stop lane adding further safety in between.

          The 33% increased road space would add to the distance between vehicles. It would reduce: impact & congestion, engine & road wear, road repair & fuel consumption. Speeds would be smoother & journey times much shorter.

          The expense of the obstructive central barrier would be saved, & emergency assistance could cross to the opposite side of the motorway without a protracted detour.

          The method could provide the benefits of the M4 widening, without the long-enduring expensive complication of widening.

          If any query remains, I can respond further.

Comments are closed.