The Ocizla roundabout was built in the first quarter of 2021 of prefabricated elements. Due to inadequate placement of the roundabout, traffic accidents began to occur in which motorcyclists were predominantly involved. When driving towards the Ocizla roundabout, drivers are not able to keep the lane. Instead of following a slight right curve to enter the roundabout they drive straight ahead until entering the opposite lane or crash on the curb stone of the roundabout. The accident data and the results for traffic monitoring give strong evidence that the cause of the accidents cannot be technically explained. It is rather a question of Human Factors of space perception that has to be investigated to solve the problem.
A traffic monitoring between 6th and 8th October 2021 with a representative sample of 156 vehicle was conducted. We detected 23% of vehicles that run near to the centreline or even crossed it. The Human Factor Evaluation Tool (PIARC) showed a high Human Factors Risk Score. According to that only 32% of drivers demands were met.
Consequently, Human Factors countermeasures have been planned and implemented. A first evaluation showed a significant improvement of the Human Factors Score: 76% of drivers demands are fulfilled after implementation of countermeasures. This is a very good result – achieved only by low-cost optical measures without substantial building changes of the Oriza roundabout.
The rehabilitation of an accident site with Human Factors is an effective way if accidents are not caused by technical issues but by wrong orientation, perception or even wrong expectations regarding the situation. It allows a pro-active approach to road safety.

Human factors; road safety; low-cost measures to improve road safety