Highways Agency

The Project

The eastbound carriageway of the A30, which carries trunk road traffic from west Devon and Cornwall, meets the M5 at Junction 31 on the south west side of Exeter. The A38 from Plymouth and south east Cornwall also meets the M5 at this point.

During normal traffic conditions for most of the year, the slip road carries an average of 14750 vehicles per day. These join an M5 northbound flow of 34000 vehicles per day. However, on a summer weekend in August these figures can rise to 26000 and 59000 vehicles per day, respectively, with much of this being concentrated into the late morning, afternoon and early evening. This has resulted in traffic queuing for up to 14 km (9 miles), with occasional delays of over 60 minutes. 

We carried out some alterations to the junction in 2005/2006 following a traffic modelling exercise which guided the design. Whilst the scheme was successful in improving the operation of the merge with the motorway, the anticipated queuing results were not achieved. We monitored traffic queues and behaviour following the works and listened to comments received from members of the public.  As the result, it was decided to make more extensive modifications to the layout.

We are carrying out improvements to the junction in order to increase its ability to cope with peak traffic flows during holiday periods. The basic principle involves the provision of two lanes of traffic between the A30 (eastbound carriageway) and the M5 (northbound carriageway).

The work will mainly consist of new signing and road markings, but will also involve some surfacing, installation of safety barriers, drainage, street lighting and some bank retention.  A redundant sign gantry on the A30 will be removed.

Traffic Management

The majority of the work will be carried out at night in order to avoid disruption to traffic.

There will be some times when we will have to close the road. The exact nights involved will be well publicised in the local media.

During night time closures, A30 eastbound traffic will be diverted as follows:

• Traffic wishing to access the M5 northbound will be directed to exit at Alphington Interchange and follow Alphington Road (A377), Marsh Barton Road, Bad Homburg Way (B3123), and then the A379 to rejoin the M5 at Junction 30.
• Traffic wishing to access the A38 southbound will be directed to use Alphington Interchange and follow Alphington Road (A377), Marsh Barton Road, Bad Homburg Way (B3123), A379 to rejoin the A38 at Wobbly Wheel Junction.

As there are height restrictions on the diversion route, any vehicles above 16 ft. high will be directed through an alternative route.

Following successful trials during the summer holiday season in 2007, we are now moving on to design and build the scheme detailed above. Until this is achieved, in Autumn 2008, the temporary arrangement will remain in place.  As the road will not be up to the full standard until the project is completed the temporary 50mph speed limit will remain in force.