Controlled motorways offer improved travel time reliability and less stress for drivers, but in some cases costs can outweigh benefits.

Experience of controlled motorway deployment on the M25 in the United Kingdom.

November 2004
London,United Kingdom

Summary Information

This report provides a summary of the work undertaken and key results from various Controlled Motorways studies to evaluate the Controlled Motorways installation on the M25 from junctions 15 to 16. The basic principle of Controlled Motorways is congestion management. Key features of these facilities include: mandatory speed control using variable speed limits, automatic signal setting in response to traffic conditions, and provision of speed enforcement using automatic camera technology.


The costs of Controlled Motorways outweigh the benefits for the M25 Junction 15 to 16 section. This is because traffic volumes are high enough to activate the system to slow traffic, but they slow traffic to the point it causes more delay than it prevents. The M25 also has Controlled Motorways between junctions 10 and 15, so the segment investigated in this report may benefit from that installation. It is acknowledged that there could be benefits from applying Controlled Motorways at other sites. The primary benefits identified for Controlled Motorways are:
  • Smoother and more reliable travel time at certain times.
  • Reduction in stress for drivers.
  • Reductions in the number and severity of accidents.
  • Reductions in traffic noise, vehicle emissions, and fuel consumption.
  • Improved driver behavior.
Additional monitoring and evaluation is needed to determine if there is an economic case for investing in Controlled Motorways.

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M25 Controlled Motorways Summary Report

Author: Department for Transport

Published By: Department for Transport

Source Date: November 2004



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Typical Deployment Locations

Metropolitan Areas


photo enforcement, speed cameras, automated speed enforcement, automated enforcement, photo radar, coordinated signals, signal coordination, centralized signal control, signal synchronization, traffic signals, advanced signal control, signal timing optimization, coordinated signal control, advanced signal controller, traffic signal retiming, retiming, VSL, managed lanes, customer satisfaction, freeway management, cost

Benefit ID: 2015-01032