M25 Speed Harmonisation

The M25 Speed Harmonisation project was a highly effective congestion management tool, installed on the anti-clockwise section of the M25 between Junction 28 and Junction 27. An innovative approach was taken, combining pVMS, SPECS type ANPR cameras, a central Journey Time Management Server (JTMS) and wireless General Packet Radio Service (GPRS) communications. The JTMS would anticipate flow breakdown by monitoring average vehicle speeds and traffic volumes. If such conditions occurred advisory 50 miles per hour (mph) limit would be displayed on five roadside pVMS. During its operational period it reduced congestion and minimised flow breakdown. In conjunction with the positive effects on congestion no injury collisions were reported during the operational period.