Highways Agency - Safe roads, Reliable journeys, Informed travellers

Background

The anticlockwise section of the M25, between junctions 28 and 27 was identified as a section of road where congestion occurs on a regular basis.

Reducing traffic speeds during high usage periods prevents the stop-start conditions familiar to many drivers.

The Project

This innovative trial project based on the deployment of Automatic Number Plate Recognition (ANPR) cameras, coupled with roadside portable Variable Message Signs (VMS), was implemented on the M25 between junctions 28 and 27.This is combined with locally installed technology known as a Journey Time Management System (JTMS). This is the first time that existing Highways Agency approved technology has been combined in this way to achieve benefits for road users.

The aim of the project was for the ANPR to detect increased traffic flows and then, through the JTMS set the advisory reduced speed limit of 50 mph. This created a smoother traffic flow at reduced speeds and increased safety, maximised traffic flow and increased journey time reliability.

The ANPR cameras were used for gathering flow and journey time information. The information they captured was used to drive signals and was not for enforcement purposes.

Six ANPR cameras (located across 3 sites) monitor vehicle journey times on this section of the motorway. An automated JTMS analyses the journey time data. When the JTMS detects a congested motorway it will set an advisory 50mph speed limit on the five portable VMS located next to the hardshoulder.

Portable VMS had the added advantage of being able to display other messages aside from the advisory speed limit of 50mph together with flashing lanterns set by the JTMS, for instance if an incident occurs drivers can be informed of delays ahead.

Trial Outcome

This project was set up as a trial. The analysis of the data obtained from the trial has shown that the combination of the ANPR technology with the Portable VMS signs has had a positive impact on driver behaviour on that section of the motorway

The objective to create smoother, maximised  traffic flow,and  increased safety have been realised by this system.

The trial scheme was removed by the  Highways Agency when the M25 J27-J30 widening works started.  The widening works will also see the installation of a Controlled Motorway system similar to that which currently exists between M25 J10 and J16.  The controlled motorway system, uses overhead gantries to set mandatory variable speed limits designed to keep traffic moving.