An 8 mile section of the motorway in Hertfordshire is the first in the country of a new style of ‘smart motorway’ schemes where pioneering technology and use of the hard shoulder as a permanent running lane combine to reduce congestion and ease traffic flow, improving the reliability of journeys.
One more section on the southern part of the M25 is due to open next month, with a third later in the year on the northern section, with similar schemes being rolled out across the country including the M1, M3, and M62.
Smart motorways deliver additional road capacity more quickly and at less cost than traditional road widening schemes, while remaining at least as safe.
Roads Minister Robert Goodwill said: "The additional capacity on the M25 is part of the government’s record investment in the strategic road network, with £15.1 billion being invested to add over 400 lane miles of capacity on our busiest motorways by 2021.
"Our motorways are the backbone of Britain and vital to building the UK economy, with approximately four million vehicles using them each day."
Graham Dalton, Highways Agency Chief Executive said: "The Highways Agency is a world class roads operator and we have built upon our experience of operating the M42 pilot scheme. The design changes have meant that smart motorways are quicker to build, more intuitive for drivers and more efficient to operate, while maintaining safety."
The improvement work on the M25 has been carried out by Connect Plus.
Tim Jones, chief executive officer of Connect Plus, said: "I am delighted that Connect Plus has achieved another major milestone on its journey to transform the M25, on behalf of the Highways Agency, into a high capacity world-class motorway with exemplary levels of safety and reliability.
"Connect Plus has implemented a range of new and innovative technology and developed new operating procedures for this section of the strategic road network. We now look forward to operating it in a safe and effective manner and to completing the northern action later this year."
Work to convert this section of motorway, between junctions 23 and 25, to smart motorway began in February 2013; temporary narrow lanes have been in place to keep three lanes open to traffic in either direction at peak times and to create a safe working environment.
Construction on the second section of this scheme, between junctions 25 and 27, has already started and is due for completion towards the end of 2014.
Meanwhile a similar scheme, between junctions 5 and 6/7 has completed construction and after a period of essential testing and commissioning of systems, is due to open next month. This is ahead of the original planned completion of December 2014 and follows a reprogramming of the work schedule, and good weather. The hard shoulder will be a permanent running lane between junctions 5 and 6 with a traditional hard shoulder between junctions 6 and 7 where there are already four lanes available to traffic.
The new technology has been added to the road to provide drivers with safe and reliable journeys. This includes infrared CCTV, being used for the first time by the Highways Agency, to enable staff in the control centres to have increased visibility of the network and will be able to respond even quicker to incidents.
The section between junctions 23 and 25 also includes:
Road users can find out more about how to use smart motorways by visiting the Highways Agency’s website