Highways Agency

Making better use of the trunk road network

Overview

The 6,500-mile trunk road network - which includes 2,000 miles of motorway - accounts for less than 4% of England's roads, yet is used for a third of all road journeys and half of all lorry journeys.

Forecasts show that this level of pressure is likely to grow and that traffic could almost double by the year 2025 if demand for road space is unconstrained. At the same time, the resources and space available to build and improve roads are limited. It is therefore important to get the best out of the existing network.

One of the best ways of achieving this is to introduce more sophisticated traffic control and network management techniques. At present, the trunk road network is only congested for limited periods of time. This is due either to peaks in demand, when a great many motorists want to use the same length of road at the same time, or because of temporary lane restrictions caused by accidents or road works.

Improved driver information can help to alleviate congestion by providing motorists with details of current and expected road conditions and real-time - or 'as it happens' - advice on the best route to take. If only a small percentage of motorists can be encouraged to use alternative, less-congested routes, or travel at a different time, or not travel at all, then the benefits could be significant to everyone.

The change in emphasis from road-building to network management is reflected in the Green Paper Transport - the Way Forward, which recognises possibilities for making better use of the existing network at lower cost. Our Road User's Charter - part of the Citizen's Charter initiative - sets out the need to develop quality-of-service indicators which will enable us to measure the network's performance in terms of congestion, journey-time reliability and safety.

One of the key objectives of our network control policy is:

"to deliver a reliable level of service to users of the trunk road system by deployment of traffic control systems and the provision of high-quality advice and information to drivers both before and during their journey."

(HA Business Plan 1996/97)

Our strategy for managing and controlling traffic is to:

• improve road safety - and hence reduce delays due to incidents;
• improve network efficiency and journey-time reliability;
• reduce the environmental effects of road traffic;
• provide relevant and reliable traffic information to drivers.  

The road user's needs

A recent Highways Agency driver survey showed that:

• before embarking on an unfamiliar trip, more than 70% of drivers use at least one source of information about traffic conditions;
• even for long journeys where the driver is familiar with the route, 60% require some traffic information;
• the most common request from drivers is for up-to-date information on congestion and roadworks.

Road users are not always fully aware of the extent or effect of congestion upon their journeys. There is considerable demand for relevant and reliable traffic information to enable motorists to choose the best route for their journey.

Existing arrangements

Driver information services are already provided by both the private and public sectors. These include variable message signs (VMSs), radio broadcasts and in-car systems. But there is scope for considerable improvement.

New intelligent transport systems and improved information services are being developed. These include: navigation and route-guidance systems; systems to give drivers new types of information; and new ways of presenting information more clearly, to meet the road user's specific needs.

Each of these systems and services will require an up-to-date source of high-quality traffic information for a market which is just developing and has considerable growth potential.

Network management

The present - tactical network management

Tactical network management involves controlling traffic in response to localised incidents and conditions. This function is carried out by 32 police control offices (PCOs). Their role is to ensure motorists' safety by enforcing road-traffic regulations and managing traffic during incidents. Current tactical control facilities include:

• emergency telephones;
• the matrix signalling system - usually located on the central reserve of motorways;
• variable message signs;
• closed circuit television;
• on selected sections, automatic incident-detection systems that set signals automatically when traffic queues form, using a system called MIDAS;
• the controlled motorway pilot scheme between Junctions 10 and 15 on the M25. This is helping to improve traffic conditions by using variable speed limits to control traffic.

An extensive communications network, comprising copper and some optical fibre links, is used to connect all of the above systems and equipment.

Tactical traffic-management has meant that signal- and sign-switching have been controlled locally and are largely based on information about conditions on the local network. This structure works well where a quick response to incidents is required for safety reasons and the resultant traffic effects are localised. However, there is a need to deal with incidents and conditions which have an effect over a wider area.

The future - strategic network management

A more strategic approach to network management would help motorists to avoid delays by giving them information about congestion while they are still a relatively long distance from the problem - or even before congestion occurs.

We commissioned a study to look at the optimum structure for strategic traffic-management and this considered a range of possibilities. The study concluded that the most effective solution would be a two-tier structure consisting of:

• existing tactical PCOs; and
• a new strategic level - Regional Traffic Control Centres (RTCCs) - to provide additional network-wide facilities.

This hierarchy offers the advantages of:

• a complete overview of conditions on the network as a whole to enable strategic decisions to be made;
• a seamless system to permit strategic traffic control across police boundaries;
• a specific wide-area network management expertise to complement PCOs;
• cost-effective development and deployment at a limited number of RTCC sites, rather than the more expensive process of equipping all existing PCOs.

How would strategic management work?

Drivers on the M20 in Kent heading for Birmingham are faced with a number of route options. They can use the M25 clockwise to the M40, or anti-clockwise to the M1 and M6. The differences between these routes in non-congested conditions are small - around ten minutes' travel time and around ten miles' distance.

Should congestion occur - perhaps due to a major accident on the M25 - then the equation could alter significantly. By giving motorists information on the preferred route - through VMS and in-car systems - before they reach the congested area and while they can take alternative routes, a good deal of time, environmental pollution, accidents and frustration could be saved.

However, directing all of the traffic on to one single diversion route is not always the best answer - it may just move the problem from one part of the network to another, creating even worse congestion.

Strategic management therefore requires information on traffic conditions over much of the network, including alternative routes. Computer models can be used to predict what traffic conditions will be like in several hours' time, so that motorists can be warned via VMS and in-car information services.

Strategic management systems using VMS are already being put in place in Kent and in the London-Birmingham-Nottingham triangle, known as the Midlands Driver Information System.

Looking to the future

Many changes will occur in the way traffic is controlled on the road network as we head into the next century and beyond.

At present - and for the foreseeable future - the Highways Agency is focusing its activities on making the best use of the existing trunk road network. This can be done by improving the management and control of traffic in busy sections of the network and providing drivers with better advice and information to help them make decisions about their journeys.

In the longer term, a number of technological advances may arise. These may include 'intelligent roads' - which navigate vehicles automatically along routes without the need for driver intervention. Even so, information on network conditions would still have a significant role to play.

Any new initiative will need to be flexible enough so that it can be developed and adapted to support these changes as they take place.

Summary

By introducing strategic traffic management we will be able to provide motorists with information and advice about traffic conditions and the best action to take to avoid congestion. This will reduce accidents, delays and pollution.