Collective traffic management measures are operated on German Federal highways using lane control systems (LCS) and network control systems (NCS). LCS are an important part of the traffic infrastructure on Federal highways in Germany. They warn the road users about risks and hazards, and harmonise the traffic flow by means of modifiable ("dynamic") signs that can be adapted to the traffic or hazard situation in question. The signs used are traffic signs according to the StVO (German Road Traffic Regulations) such as the permissible maximum speed and warning signs. The pre-requisites for the effectiveness of such systems for traffic safety and for improving the traffic flow are to what extent the road users perceive, understand and accept the signs. For this purpose a certain number of displayable traffic signs and standardized signs for various risk and traffic situations are defined for LCS in the corresponding guidelines. Recently ideas have been developed for providing additional information in text form that should also be displayed at the same time with dynamic traffic signs. This includes additional text signs that are to be installed as a so-called character "D" under the variable message signs (VMS) in the area of LCS. When dynamic signs and their content are designed it should be taken into consideration that the human brain can only absorb and process a limited amount of information at any one time. In addition to the actual task of driving, a vehicle driver must fully register and understand the information displayed within a relatively short period of time and then must make the correct decision. The impacts of additionally installed text signs on the display gantries of LCS were examined in this project from a perception psychological, traffic law and traffic technology point of view. In this connection it was analysed whether the vehicle drivers are over-burdened or made uncertain by the additional information and whether this can lead to unintentional or dangerous driving and braking manoeuvres, or to mandatory StVO (German Road Traffic Regulations) variable message signs being ignored. Beside the consideration of possible risk potentials the impact on the effectiveness of the LCS was also analyzed. After a presentation of the results of the literature analysis, various experiments were carried out in the laboratory including an interview, an experimental drive in the driving simulator on a highway with integrated LCS and D-lines at the display gantries as well as a perception psychology post test with 60 test participants. The selection of the test participants and interpretation of the results was also oriented with regard to the various different road user requirements (commuters, frequent drivers and drivers whose native language is not German, etc.), that have an impact on how the signs are recognized and understood, and on the corresponding behavior of the road users. Literature studies have shown that limited human information processing can lead to negative consequences in driving and visual behaviour. The consequences are: - Drivers take considerably longer to read the sign and as a result also take their eyes off the road traffic for longer. - Higher proportion of speed reductions, braking manoeuvres and lane changes. - At the same time a decrease in the time spent looking at the variable message signs A, B and C. Incorrect or faulty identification of the text can lead to faulty behaviour. Both the eye tracking data from the simulation and also the results from the post-test support the findings from literature. The higher the number of characters presented and the longer the texts of the D-line are, the more inaccurate the information processing is, in particular for the D-line. It is not possible to clearly and unambiguously classify these D-lines as additional panels or prohibitory or restrictive signs. In addition they are in conflict with the present design principles of the corresponding guidelines introduced by BMVBS. Furthermore the introduction of the D-line would lead to a mixture of the separate systems of section management and network management that have proved successful and are well-known in Germany. From the point of view of the results and findings from perception psychological, traffic law and traffic experiments and testing, a D-line cannot be recommended for Federal highways in Germany. This report also contains an appendix and they can be consulted at the Federal Highway Research Institute. For the readers Information, the references to this appendix has been retained in the report text. (Author/publisher)
Samenvatting