Under the plans, junction 25 of the M25, where the motorway meets the A10 in Hertfordshire, will have extra lanes created on its roundabout, widened approaches on the M25 and the southbound A10, and new a free-flow lane between the clockwise M25 to the northbound A10.
The Highways England website puts the cost at £25m to £50m and the start date as March 2020.
The scheme is designed to improve journey times through the junction and allow more capacity on the exit slip roads; reducing the likelihood of traffic queuing back onto the M25, particularly into the Holmesdale Tunnel.
A public consultation on the options was held from 16th January to 28th February 2017 and 413 responses were received; 92% agreed that improvements were needed at the junction, and 77% backed outlined proposals for the upgrade.
Highways England project manager Piotr Grabowiecki said: “It’s great to see that there is clear backing for the improvements, and now we can move on to developing a detailed design for the upgrade. There will be another opportunity for anyone interested in the scheme to have their say in next year, when we put the final plans to people for their views.”