8. Design for Road user Characteristics and Compliance

Key messages

• Human factors is a well-established scientific term in use since the 1930s by the safety community of man-machine-interaction. Human Factors is defined as those psychological and physiological threshold limit values that are verified as contributing to operational mistakes in machine and vehicle handling.
• Unless roads are designed and managed to take account of human factors, it is unlikely that a Safe System can be achieved.
• Speed management is one key step towards creating a Safe System. Speeds are the result of road design and the resulting subconscious choices made by road users. Speed can be heavily influenced by the number of contrasts in the periphery of the field of view (e.g., by signs and markings), by the size of the visible road surface and the distance of the fixation point in the depth of the field of view.
• Two additional and until yet not systematically practiced key steps are the management of the field of view and the pre-programming of drivers expectations. That's why road engineers have to be trained in psychological basics of activity regulation (perception, cognitive processing and motor response).
• A skillful combination of design elements can create ‘self-explaining’ roads where appropriate actions, including speed choice, are obvious to road users. Self-explaining roads lead road users to behave in a way that road planners and designers expect, thereby resulting in low crash rates.
• In addition to road design, a range of techniques for directly influencing road user behaviour are available, including education, publicity and enforcement.
• Good practice in each of the above areas is now well-understood, and guides to good practice are available.