The importance of traffic information is increasing as the road systems become even more congested. Further development of the technologies and services requires investment which, particularly in view of today’s limited financial resources, calls into question the effectiveness and the benefits of traffic information time and time again.
This research project is an attempt to find answers to the causalities of traffic information, the effects on road users and road travel and their factors of influence. It endeavours to describe and quantify the benefits of traffic information and includes recommendations for improving its effectiveness and enhancing these benefits. The investigations cover dynamic, situation-dependent traffic information and deal with the various distribution media, such as radio, navigation systems, mobile communications, etc. They do not cover variable message signs installed on the road network.
After evaluating the literature, the first task was to identify the fundamental chain of effects and the generation of benefits. This formed the basis for establishing the measurement and survey concept, using two typical stretches of road: the A1 Berne/Grauholz and the A1 Winterthur bypass.
The measurements involved, among other things, identifying traffic diversions due to a revised choice of route resulting from congestion messages. In the case of the A1 Winterthur bypass, interviews were also conducted with motorists delayed in traffic jams.
The results were compared with the findings of an unrelated domestic survey conducted by FEDRO, the Federal Roads Office. In both cases, those interviewed were asked to give their opinion of traffic information, their response to the traffic information they received and their personal evaluation of the benefits of traffic information. Whereas the domestic survey was concerned with different types of traffic information, the focus of the survey of motorists delayed in traffic jams was directed towards the effects of traffic information in conditions of road congestion.
The findings from the case histories are at different levels. They relate to different factors of influence, such as the distribution of traffic information, the range of effects, the preferences of road users, the quality of the traffic information and the feasibility of quantifying its effectiveness.
Distribution of information or gaining access to road users: Despite the fact that a significant majority of those interviewed regularly listen to traffic information broadcasts on the radio, only a minority hear the messages in time to take alternative action. Moreover, it was confirmed that accessibility and frequency of use of traffic information is dependent on the purpose of the journey and the number of kilometres travelled each year. Traffic information is accessed more frequently during time-sensitive journeys made by commercial and professional drivers than by road users engaged in holiday or leisure travel.
Range of effects: Traffic information works in two ways. On the one hand, traffic information causes road users to change their behaviour and this is reflected in the form of changes of route or in an increased alertness on the part of drivers. These effects can result in driving benefits, for example a change of driving style, accompanied by increased road safety. Almost 100% of drivers receiving traffic information alter their driving style accordingly. Messages indicating road conditions or warning of particular hazards are highly appreciated. On the basis of the analyses conducted, reports of vehicles on wrong carriageway generate an annual financial benefit of at least 1 million CHF. On the other hand, the majority of those interviewed stated that it was also valuable to be simply kept informed about the traffic situation. These effects operate at a personal level; they cannot be viewed or quantified ‘from outside’ and do not result in any alterations to traffic conditions. Instead, they are of purely individual benefit − the opportunity to inform others for example.
Individual preferences on the part of road users: Those obtaining information react differently according to their own personal opinion and the actual situation. The majority of those interviewed who are notified in good time before being involved in a traffic jam and who, as a result, have a variety of response options open to them, either regard themselves as committed to their modes of transport and/or journey times, or are unable to adopt any other response whic