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M25 Junction 12 and M3 New Road Layout
M25 Junction 12 and M3 New Road Layout
- Status
- Current
- Located in
- Area 5
- Scheme type
- Other
The Project
On 5th March 2007 we implemented a change to the road layout designed to try and reduce overall delay at junction 12 of the M25.
The Highways Agency has now reviewed the results of the new trial road layout at this junction.
The trial has shown a significant journey time reliability improvement, therefore we have decided to make the scheme permanent, however the final decision about making the trial permanent including the implementation of the 50 mph speed limit will be subject to a statutory consultation, expected to take place over a 12 week period this summer. If successful the cones and temporary signs will be replaced with permanent signs and markings.
Records showed that high volumes of traffic wishing to join the M3 westbound from the M25 anticlockwise at peak periods caused congestion and tailbacks onto the M25. In the evening peak period, approximately double the volume of traffic joins the M3 westbound from the M25 clockwise and anticlockwise than is already on the M3 westbound (from London).
On a typical weekday 32,000 vehicles travel on the M25 and join the M3 Coast bound compared to 20,000 vehicles travelling on the M3 past the M25/M3 junction.
To improve these conditions, the revised layout provides an upgraded entry slip onto the M3 westbound. This consists of two dedicated lanes for traffic joining from the M25 and a single lane for M3 westbound traffic.
Therefore, at the merge the single lane of the M3 is joined by two dedicated lanes from the M25. After this point, the M3 westbound continues as a three lane motorway.
Throughout the revised layout there is a speed limit of 50 mph and average speed cameras are in effect for your safety. The reduced speed is necessary over the length to the east and west of the schene to enable vehciles to move safely into the required lane In addition, a vehicle activated sign has been erected on the M3 to warn drivers of the approaching 50 mph speed limit.
Whilst some congestion on the M3 approach to the new layout has been generated in the evening peak period, traffic monitoring and analysis carried out since implementation has confirmed that this is far outweighed by the reduced congestion on the M25 anticlockwise approach.
Overall, the revised layout has delivered a net journey time benefit of 297 Vehicle Hour Delay (VHD) saving hours per weekday or 77,000 VHD per year saved over the original layout and the results of the customer satisfaction survey have confirmed more road users being in favour of the revised layout than the original layout.
To deliver benefits to road users, the revised layout has been marked out in traffic management. This has not only provided immediate delivery but also allowed us the option of reinstating the original layout. We are currently in a transition phase and moving towards the permanent solution.
A PDF version of the final report can be downloaded below:
