M25 Widening Junctions 23-27 (Smart Motorway)
Hertfordshire, UK · 2012–2014 (Junctions 23-25 opened 2014; part of wider M25 Smart Motorway program) · N/A (Specific cost for J23-27 not readily available, part of larger M25 Smart Motorway investment)
The judgement call
Account-gated at launchThe project aimed to increase capacity and improve journey reliability on a critical section of the M25. - It was part of a broader strategy to use Smart Motorway technology to manage demand and reduce congestion without traditional physical widening. - The scheme demonstrated the challenges and benefits of upgrading existing motorways to Smart Motorway standards. - Post-opening evaluations have been conducted to assess the effectiveness and safety of the scheme.
Key engineering challenges
Widening a highly congested section of the M25, one of Europe's busiest motorways, while maintaining traffic flow. - Implementing Smart Motorway technology, including all-lane running and variable speed limits. - Managing complex interfaces with existing infrastructure and numerous junctions. - Minimizing disruption to commuters and businesses in the South East.
Project facts
- Client / owner
- National Highways (formerly Highways England)
- Lead contractor
- Balfour Beatty (for J23-25 section)
- Lead designers
- N/A (Design integrated into project delivery)
- Project type
- upgrade
- Scale
- Widening of M25 from three to four lanes; conversion to Smart Motorway with all-lane running; installation of new technology.
- Disciplines
- civil; intelligent transport systems; electrical; environmental
- Standards & frameworks
- DMRB; CDM Regulations; Smart Motorway All-Lane Running standards
Sources: Balfour Beatty (https://www.balfourbeatty.com/what-we-do/projects/m25-motorway-widening/) - National Highways (https://assets.publishing.service.gov.uk/media/5e6a1a89d3bf7f269e22a142/M25_J23_J27_POPE_OYA_with_foreword_FINAL_Jan_2020.pdf) - Driving Change (http://drivingchange.org.uk/disappointing-economic-benefits-from-widening-the-m25/)