Abstract

The paper demonstrates that changes in the design of approach and bridge are significant for drivers and can interfere with correct visual perception. This conclusion is a result of analysis performed in three stages. The first stage is an investigation of road accidents on bridges. The accident factor related to bridges was greater than accident factor related to roads. The main results of accidents on bridges were collisions with parapets, guardrails, pedestrians and back-to-front collisions. The police investigations couldn't explain reasons of many accidents. The conclusion was that the cause of unexplained accidents can be an inappropriate design of approaches and bridges. The second stage is the analysis of driver preferences. It was prepared as a survey, with questions about: • the feeling of differences in driving on roads and bridges, • preferences related to location and marking of curbs, parapets, guardrails and • obstacles on bridges (making the driving difficult and dangerous). Obtained data show that the influence of some of the bridge equipment is significant in relation to differences in driving on roads and bridges. The third stage is the analysis of visual perception on four different roads with bridges. The films of driving along these roads were presented in laboratory for ten participants. Each participant had the eye movement measuring system mounted on the head. During this test eye movements were recorded by the measuring system. Next, the eye movements were analyzed for each bridge and approach. According to the design and equipment parameters on each road and bridge, differences of eye movements (the density of sacades) were found. Through statistical analysis, the equation in order to relate the density of sacades to the design and equipment parameters was created. For correct visual perception the following factors are significant: the visibility, lane width changes, the road and bridge curvature, the distance between driver and guardrail, visibility limitation due to guardrail, sideway obstacles (curbs, parapets, guardrails, narrowness) and the bridge visibility.