Keep traffic flowing with 2nd Generation Ramp Metering


2nd Generation Ramp Metering (2GRM) to keep traffic flowing smoothly

Since 2006, Highways England has benefited from deploying Ramp Metering (RM) as one of its principle Traffic Management techniques, and has deployed the Dynniq 1st Generation RM system (1GRM) at 90 junctions across the national network. Fourteen years later, Highways England commissioned Atkins and Dynniq to specify, develop and trial a new generation. The evolved 2GRM system is better adapted to the current and future traffic environment, and facilitates more collaboration between different traffic systems and traffic authorities.

Approaching the limits

First implemented in the United States, Ramp Metering is a proven technique for addressing congestion where slip road flow is a problem. Too many vehicles joining too quickly can cause congestion, slowing down traffic flow. To avoid this, lights keep traffic flowing on motorways and highways by controlling the rate (flow) of vehicles joining from the slip road. However, fourteen years after its implementation in the UK in 2006, the 1GRM system is becoming hard to maintain. Its static algorithms cannot keep up with changes unless an engineer recalibrates them every few years. Also, the necessary roadside infrastructure and civil work for a loop system mean that there are certain locations where it cannot be deployed.

Exceeding the limitations

To retain and enhance the benefit of RM, whilst also addressing these drawbacks, Highways England commissioned a trial of a 2nd generation of Ramp Metering system (2GRM). Our role was to design the new system, and then develop, test, deploy and maintain it. This is the kind of innovative challenge we are best at, and our focus was specifically on developing self-optimisation and improving two-way interfaces. Atkins, a multi-national firm of consulting engineers, acted as Highway England’s representative and they were responsible for activities such as specification of requirements, programme management, project delivery, stakeholder liaison and project evaluation.

The resulting new and evolved system uses wireless magnetometers, adaptive algorithms plus improved and open interfaces. All these new features are aimed at cutting costs and increasing flexibility. For example, the battery powered magnetometers don’t require extensive provision of cables, power supplies or communication. Without this form of technology it would not have been feasible to deploy 2GRM at a site on the A3 in Guildford, which is now the 1st trunk road that Highways England have instrumented. Manual recalibration is reduced or eliminated by adaptive algorithms continually adjusting key parameters to maintain optimum operation at each site under changing traffic conditions. New algorithms (from any vendor) can easily be added and made operational for any site. With cloud technology and third-party interfaces, the 2nd Generation system can be controlled centrally and remotely, and authorised traffic management systems can connect to exchange data and control. All in all, 2GRM does everything the first generation did but delivers improvements in the deployment, operation, integration and expansion of Ramp Metering.

Trial sites

After we successfully completed the design, development and testing stages, 2GRM went live at two trial sites in the UK: the A3 Southbound at Dennis interchange, Guildford, and the M25 Junction 13 Northbound, near Heathrow. The infrastructure was successfully completed, and the system went live in September 2018 and January 2019, respectively. Operation at both trial sites is independently reviewed by Atkins (at 6 and 12 months after go-live) and reported to Highways England to inform their future plans for Ramp Metering across their network.