This road project has now been completed. This page will be available for 24 months from the date of scheme completion, after which time you will only be able to access this information on The National Archive version of this page.

M25 Junctions 23-27: Smart Motorway

Project status:   Completed

Start date:   February 2013
End date:  November 2014

Type:   Major Scheme
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Major Scheme

Part of our programme of improvements (value >10m)

Cost:  £180 million (subject to final accounts)


Where was the project located?

This SMART motorway scheme was carried out on the M25 between junctions 23 and 27

Why was the scheme needed?

The M25 is one of Europe's busiest motorways, handling around 200,000 vehicles every day. It is at the core of our network and is suffering from increasing congestion levels and journey times. We need to manage traffic flows better and to help achieve this we have already widened the carriageways from 3 to 4 lanes in each direction on the sections between junctions 16 to 23 and junctions 27 to 30.

Since June 2008 we have been considering options to improve the traffic flow from junctions 23 to 27. In January 2009 the Secretary of State decided that this section of motorway could be improved by the introduction of a system to replace the hard shoulder with a fourth running lane (otherwise known as Smart Motorways - All Lanes Running).

What work was carried out?

The section of the M25 between junctions 23 and2 7 is now running as a "smart" motorway. The hard shoulder has been converted for use as a permanent traffic lane. This, together with the introduction of enhanced on-road technology to manage traffic flow will improve the reliability of journey times, providing a boost for businesses and the economy.

How did this benefit road users?

This project will relieve congestion and smooth the flow of the traffic, while maintaining safety and improving journey times. These benefits will also support development in the region.

We already have evidence of the benefits that a smart motorway scheme can bring. The first smart motorway scheme opened to traffic on the M42 motorway in 2006. Recent analysis of the data gathered since opening has found that journey time reliability improved by 22 per cent and reduced emissions by up to 10 per cent due to traffic flowing more smoothly.

In addition, personal injury accidents have reduced by more than half (55.7%) since hard shoulder running was introduced. There was also an overall reduction in the severity of accidents with zero fatalities and fewer seriously injured.

How do I find out more information ?

If you have any queries about this project you should contact the Highways Agency Information Line by emailing ha_​info@​highways.​gsi.​gov.​uk or calling 0300 123 5000.

Site office:

M25 Smart Motorway Improvement Works - Junctions 23 to 27
Sanska Balfour Beatty Joint Venture
London Colney, St Albans

Email: communityrelationsj2​3​-​2​7​.​m2​5​@​sbbjv.​co.​uk
Telephone: 01727 744933

The office is opened between 0700 and 1900 Monday to Friday, and 0700 and 1300 on Saturday, closed on Sunday. 

Business Case

M25 Junctions 23 to 27 Managed Motorways - Business Case
Business Case - Information correct as at December 2010


M25 Junctions 23-27 Smart Motorway - Smart Motorways Leaflet
M25 Junctions 23-27 Smart Motorway - Get smart know your motorways
M25 Junctions 23-27 Managed Motorways - Closure Information Leaflet
M25 Junctions 23-27 Managed Motorways - Closure Information Leaflet - March 2013



M25 Junctions 23-27 Managed Motorways Newsletter No 3
Welcome to our third newsletter. Work to bring junctions 23 to 25 up to all lane running standard has been completed.
M25 Junctions 23-27 Managed Motorways Newsletter No 2
Welcome to our second newsletter. Since our last update, work to convert junctions 23 – 27 to a managed motorway has seen significant progress and is on target.
M25 Junctions 23-27 Managed Motorways Newsletter No 1
Welcome to the first report on progress to convert the M25 to a managed motorway between junctions 23 – 27.


M25 Junctions 23-27 Smart Motorways - Safety Project Control Framework Products
Safety Plan, Hazard Log Report and Safety Report for the M25 Junctions 23-27 Smart Motorways scheme.


M25 junction 23 to 27 Final Use Assessment
M25 junction 23 to 27 Final Use Assessment – Noise Insulation Regulations Assessment
M25 Junctions 23 to 27 Managed Motorways - Summary of Consultation Responses
Summary of Consultation Responses Managed Motorways – All Lanes Running M25 J23 to J27
M25 Junctions 23-27 Managed Motorways - Environmental Assessment Report
For a copy of the Environmental Assessment Report for this scheme please email the team