Incidents on the road network happen every day and can have serious impacts on road users using this network. It is expected that with a better supply of traffic information the situation of the road user can be improved in these situations. New information systems are likely to contribute to the better information supply. This research will discuss these issues and will focus on the information needs of road users in case of incidents. Furthermore, it will review how road users respond to this information. The main objective of the research is:

Reveal road user preferences towards traffic information in case of incidents on the road network and review if different information policies have different effects on route choice.

In this research incidents are defined as: events that happen unexpectedly and cause a reduction of the capacity of the road network. Opposed to other work, there is chosen for a definition that incidents are unexpected. This way only situations which cannot be anticipated, are reviewed. The scope of the research is limited to the main road network in the Netherlands. The main road network in the Netherlands consists of motorways (no level crossings, 4 or more lanes and maximum speed 120 km/h), expressways (level crossings, 2 or 4 lanes and maximum speed 100 km/h) and highways (level crossings, 2 lanes and maximum speed 80 km/h).

The following main research questions were formulated:


Why do road users request traffic information in case of incidents on the road network?


What are the effects of incidents on the road network for road users?


What is the current state of the information supply to road users about incidents on the road network?


What are the user preferences and responses towards traffic information in case of road incidents?

The first three research questions are answered by conducting a literature survey and a review of grey literature.

From this research it can be concluded that road users are indeed in need information in case of road incidents to cope with ignorance, and uncertainties which are caused by these incidents. The effects of incidents on road users are considerable but different for different users. Commuters seem to have less need for information in case of non-recurrent congestion than users with business and freight purposes. This can be explained by the fact that commuters often travel in very congested periods when the possibilities of rerouting are limited. Also commuters demonstrate a lower value of time (in terms of money). The consequences of non-recurrent congestion can be much more serious for users with business and freight purposes. For these groups the time of arrival is often far more important. The need for traffic information incase of incident situations for users with other purposes depends on whether time of arrival of the trip is time-bound or not.

At the moment different systems are available to detect and measure congestion. The current systems can acquire reasonable and frequently updated information. New technologies, e.g. based on floating car data, are expected to bring more accuracy and a more complete picture of the traffic situation. Disseminating systems however often cause a delay and degradation of the information. E.g. the most used information system is radio broadcasting and traffic information by radio is broadcasted only once every half an hour and the content is very limited. New information systems are very likely to improve this because of a more extensive and frequent information supply.

It is difficult to give an estimate of the current effects of traffic information in incident situations. A comparison with a situation without traffic information is virtually impossible. Comparisons between different information strategies and stated preference researches show that traffic information does have a positive effect.

To measure the user preferences and responses towards traffic information (as mentioned in research question 4) an Internet survey was developed and conducted (159 respondents). The survey is divided into three parts. In the first part general information about the respondents is obtained (i.e. gender, age, purpose and frequency of road use). The second part focuses on the current use of traffic information, the preferences towards (future) traffic information and driver responds towards traffic information. The last part of the survey consists of two cases where respondents were confronted with different incidents with different information available. The respondents were asked how they would respond to that situation in terms of route choice. The first case was based on the ring road around Rotterdam and the second on a fictitious network. In both cases various situations with different incidents, information and trip purposes were proposed and respondents were asked how they would react. Respondents were also asked about their preferences towards the type of information which they like to receive in these situations. By using a case with an existing network and a fictitious network differences in response of users that are familiar or unfamiliar with the network can be distinguished.

The results from the internet survey confirm that road users are in need of traffic information, especially in the case of incident situations. In these situations road users want more than the ‘ordinary’ information (location and length of jams) disseminated by radio broadcasts. Information about travel times and in a lesser extend delay times are most popular among all road users. Also there are some group specific preferences (see table 1):


More preferred (+)

Less preferred (-)


Description of best alternative*



Length and location of jam(s)

Description of the incident





Description of the incident

Length and location of jam(s)



Description of best alternative


Less freq. users



Frequent users

Length and location of jam(s)


Very freq. users

Length and location of jam(s)


*Only in case the commuter is not familiar with the network

Table 1: Tabular representation of road user preferences towards traffic information in incident situations (without delay and travel times).

The different road users also respond differently to information in terms of route choice. Also, different information strategies in case of the same incident can have different effects on the route choice behavior of an individual road user. This suggests that a better traffic information supply is needed in case of road incidents, because the current supply is not sufficient. More personalized traffic information in case of road incidents might be desirable because different road users have different preferences.