How to parallel widen a motorway

Kindly contributed by Paul Tebbett, who was involved in the scheme illustrated.

Many of the country's motorways (and major roads, for that matter) were built to cater for the traffic volumes of their era. Unfortunately, the car boom has meant that a lot of roads are simply not able to carry the numbers of vehicles we see nowadays.

Who could have guessed there would be over 30 million cars on the road today? Even more so back in 1950, when the figure was a mere 3 million. Then again, not many people would have thought there would have been 14 million in 1976.

Changing travel patterns, the closure of railways, and the desire to venture further for family holidays have all added to the problem.

The best solution would be to build new roads - but there are only so many that can be built. The next best thing would be to widen existing roads. In the case of motorways, this would often be fairly easy as it could be done within the boundaries of the existing road.

For many motorways, widening would be much easier by building a new carriageway alongside the existing road. The original road could then be reconfigured as needed, sometimes providing extra space in case further widening is needed in future.

Between 1980 and 1994, the M5 was widened, in stages, to three lanes between junctions 3 and 8. This stretch was somewhat unusual in that it was built as a two-lane motorway, when most motorways had previously been built with three lanes each way (including the M5 on either side of this section).

This collection of photographs shows the progress of the M5 widening between junctions 4 and 4A at Lydiate Ash, and were taken in around 1988 / 1989.

 

The before...

M5 before widening

Looking northbound just beyond the northern end of the widening works.

At this point there is an extra lane northbound, this being a crawler lane added in 1975/6 due to the presence of a steep climb. It gives an impression of how the road was before the whole two-lane section was widened.
M5 before widening Another northbound view of the M5, taken from further up the hill. The grey panel on the bridge is a temporary sign advising of the restrictions on the road ahead. 
M5 approaching the works A southbound view taken from the other side of the bridge - the front of the temporary sign can be seen, as can the end of the northbound crawler lane, to the right of the green lorry.

 

The during...

M5 widening

Stage one:
Before work can start properly, preliminary preparation needs to be made. This would involve the installation of fencing to mark the new highway boundary, and the clearance of any vegetation within the site. Where suitable, access points into the construction area need to be set up. These will need to be "plugged into" the local road network, reducing the number of slow vehicles entering or leaving the motorway.

 
M5 widening

Stage two:
New earthworks will need to be constructed alongside the existing carriageways, also creating a flat surface along the course of the new carriageway. Any existing bridges and culverts running under the motorway will then need to be extended to run under the full width of the widened road.

  
M5 widening

Stage three:
At this point, it is time to start thinking about laying some new asphalt. However, to do this, the existing road width needs to be maintained. To do this, a contraflow will need to be set up with one lane moving onto the opposite carriageway. Once done, the vacated lane and hard shoulder can be torn up to allow the new central reservation to be installed. Also, the new bridges can be built as there is now room to position the new central piers.

  
M5 widening

Stage four:
Once the new overbridges are built, the roads concerned can be moved onto their new approach alignments. Once they are opened, the old bridges can be demolished, but this needs to be carried out with a full overnight closure of the motorway. Following this, the abutment can be removed to allow the missing parts of the new carriageway to be built.

  
M5 widening

Stage five:
The new carriageway is complete, so the contraflow can be moved over onto the new section. At this point, the opposite bridge abutment can be removed, with the space landscaped to match the rest of the environment.

  
M5 widening

Next, the old road is completely removed, and a new carriageway is built in its place. The original sections of any bridges running under the carriageway are refurbished or replaced, in order to tie into the new parts.

At the same time, the central reservation is completed, with barriers and installed along it, and along the side of the carriageway where needed. Lighting is also installed where required.

  
M5 widening at ground level

This is the view of the above location taken from ground level - at this point, the old bridge is yet to be removed.

Once the works are complete, the whole motorway can then be fully reopened to traffic.

  

 

The after...

M5 at Lydiate Ash, 2009

This photograph shows part of the widened section in 2009, ironically with the barriers and lighting undergoing replacement.

Photo by Roy Hughes and used under a Creative Commons Attribution 3.0 license.