Positions

Traffic signs are mainly intended to inform road users about how they are expected to behave and to warn them of possible hazards. It is a frequently recurring question if locations do sometimes not have an excess of signs that therefore have a confusing effect on drivers. A subsequent question is to what extent safety would be threatened if part of the signs or all the signs would be removed. SWOV wants to answer this question from the angle of the effect on traffic behaviour and safety, and not from a legal perspective which is aimed at the question of guilt and liability in crashes.

Research

So far there has been remarkably little research into crashes that are a consequence of an excess or a lack of traffic signs. Research has, however, shown that a driver only spontaneously notices 10 to 20% of the traffic signs he passes. This suggests that traffic signs can only make a small contribution to road safety. Experienced drivers indeed seem to prefer being guided by natural clues on the road and its surroundings, without feeling a need for traffic signs. However, signs remain necessary for road safety – at least for important traffic rules like speed limits, indication of access or no access, driving direction, position on the road, and priority. These rules are so crucial for the prevention of dangerous situations that all must be done to convey that particular message to all road users (experienced as well as inexperienced) and under all circumstances (good as well as bad visibility). This information will always need to be given explicitly at the times and places where the road user indeed needs the information. There is a stronger need for this information when the surroundings do not sufficiently contribute to the required safe behaviour. In those cases, traffic signs and road markings are important aids. It seems difficult to understand how just removing these aids will contribute to road safety.

Different parts of the surroundings have been shown to have a great effect on (the ability of) rapidly observing traffic signs. These include the amount of traffic, the number of traffic signs per road distance, interfering background images, and other messages from the surroundings that support or contradict the sign's message.

To counteract disturbing influences, some general recommendations can be made about the design and positioning of traffic signs and about the layout of the surroundings (e.g. advertising at the roadside) during the day and at night. However, further research is required to devise new rules.

The following possibilities could be used to improve the contribution of traffic signs to road safety:

• discriminating between important traffic signs and less important traffic signs; research has to show how the distinction can be made and how other information for the road user could be used to compensate for the removal of less important signs;
• further study of the design of traffic signs from the viewpoint of conspicuousness, recognizability, and understandability;
• considering the possibility of placing speed limit signs at all beginnings of roads, road sections, or area's, with repetitions whenever required;
• generally supporting the traffic signs' message by using other, more natural leads, which will result in strengthening the credibility of the signs' message;
• carrying out research of the effectiveness of replacing a proportion of the traffic signs with traffic signs with a time-determined message.

Position

If too many traffic signs are placed at a certain location, the signs that must really be noticed are not conspicuous any longer. Reorganization of those situations and hence removal of the superfluous signs is then desirable. A distinction in the conspicuousness of important and less important traffic signs could also be made. It is necessary, however, to first investigate to what extent there is an excess of traffic signs in the Netherlands and to how many and to what type of crashes this is responsible. It is also useful to investigate if it is possible to remove traffic signs and under what circumstances this could be done. Thorough research will need to indicate how such changes could be made safely.  SWOV advises against making such changes without further research because there is a real chance that removing important traffic signs will lead to more crashes and casualties.