Effective road and traffic management

Written evidence from David Metz (ETM 08)

Summary

1. The main problem with traffic congestion is the uncertainty of journey time. The best way of tackling this is to provide sufficiently good predictive journey time estimates to drivers before they set out. Such an approach is increasingly feasible, taking advantage of a variety of technology developments and commercial initiatives.

Prevalence and impact of traffic congestion and likely future trends.

2. The extent and impact of traffic congestion is less than is usually supposed. Recent surveys on public attitudes to road congestion commissioned by the Department for Transport (DfT) find that over four in five adults thought that congestion was a serious problem in the country. However, only a quarter reported that congestion was a problem all or most of the time on their most frequent journey, on motorway journeys or on all journeys. [1] DfT’s measure of inter-urban congestion – journey time reliability – has been flat over the past five years at around 4 minutes delay per 10 miles. [2]

3. Trade associations often talk up the impact of traffic congestion on businesses, perhaps because this is a non-contentious issue for their members. For instance, the CBI cites an annual cost to business of £7-8bn. [3] However, congestion is found to be responsible for only about a quarter of all delays in road freight transport, and only a quarter of logistics managers regard traffic congestion as the main cause of unreliability. [4] There is little evidence that congestion has caused companies to restructure their manufacturing and/or logistic systems. Companies have been able to adapt their operations to the slow growth of congestion over time, taking advantage of IT developments and utilising the skill and resourcefulness of logistics managers. So the costs of congestion should not be over-emphasised. 

4. As regards future trends in traffic and congestion, personal daily travel, as measured in the National Travel Survey, has been steady since 1995 at 7000miles and 1000 journeys per person per year (excluding international aviation), and there is no reason to expect this to increase in the future. [5] Road freight (tonne-km) also ceased its rising trend in the mid-nineties. [6]

Alleviation of traffic congestion.

5. Experience has shown that it is not possible to build our way out of congestion. Road users take advantage of the higher speeds initially possible on widened roads to travel faster and thus further in the time they have available. The National Travel Survey shows clearly that average personal travel time has remained unchanged at about an hour a day for over thirty years. Hence the benefits of investment in road infrastructure have been taken as greater access, not time saving. The increased length of trips adds to traffic, so that congestion is little changed in the long run.

6. Road pricing is seen as politically difficult. So what options are there to alleviate traffic congestion?

7. When asked in the surveys commissioned by the DfT why motorway congestion is a problem, the main reason given is that it makes journey times uncertain. The most common action taken to avoid such congestion is to set out at a different time from the preferred time.

8. Accordingly, the main problem with traffic congestion is uncertainty, not speeds slower than free flow. Such uncertainty could be reduced by better information about expected journey times in advance of the trip, without the need to tackle congestion as such. Road users would take advantage of better information by allowing the necessary amount of time, or by changing the starting time (as they do at present, but based on better information). The aim would be to put the generality of road users in the position of freight hauliers using the latest technology (see para 3 above).

9. There are a number of technological developments that are facilitating the prediction of journey times under congested conditions, in particular, digital maps, GPS positioning of vehicles, devices for locating slow moving traffic, and computational algorithms for predicting future traffic flows. [7] Existing services to road users provide optimal routing and estimated journey times, mostly based on historic traffic data, but increasingly using real time data. There are now offerings that include predictive traffic information.

10. The predictability of journey times depends on the variability of traffic flows. Advantage can be taken of developments in the management of the road network, including variable speed limits, ramp metering, and swift incident management. These measures promote the smooth flow of traffic, both to optimise system efficiency, the traditional reason for introduction, but as well to improve the accuracy of traffic forecasts.

11. There is a significant amount of activity in both private and public sectors aimed at providing better information to travellers, but uptake is slow. Building on current experience, there is a scope for a governmental initiative to foster the development of technology applications that would lead to the more efficient use of the road network. Research is needed to develop models which might be used to estimate economic benefits, and data in respect of behavioural responses to traffic information that would be needed to calibrate such models. Accordingly, there would be a case for a research initiative designed to advance our knowledge of these matters, as well as to explore a public/private approach to deployment.

Recommendation

12. A government initiative would be desirable to assess the benefits to road users of predictive journey time information and to explore a public/private partnership approach to deployment of the relevant technologies.

January 2011