Crash Compatibility between Roadside Infrastructure and Passenger Vehicles: Improving the Geometric and Structural Compatibility to Reduce Fatalities

Licentiatavhandling, 2004

Roadside accidents cause a significant number of fatalities each year in the world. To reduce this type of accident, roadside infrastructure needs to be investigated to improve protection to different kinds of passenger vehicles during crashes. Accident statistics have revealed ditches and guardrails as the two main roadside safety features that reduce fatal injury risks. Guardrails were chosen for this investigation. Geometric and structural compatibility in collisions between vehicles and guardrails were studied to find ways to improve roadside safety. Two studies on this type of crash compatibility were conducted using the computer simulation tool LS-DYNA. Full-scale crash tests were compared with the simulation results for validation. A compact car and a W-beam guardrail were chosen for a study of their interaction during oblique collisions. The goal was to investigate the influence of vertical position and stiffness of the main crashworthy structures in a vehicle of a constant mass during an oblique crash with a W-beam guardrail. The simulation showed good agreement with a full-scale crash test. Using validated models, a parameter study for the geometric compatibility between passenger vehicles and road barriers was carried out. This study concluded that the cross members of a vehicle must be stiff. A laterally weak vehicle is likely to be more severely damaged, with higher risk of injury. Moreover, a more deformed guardrail and a less deformed vehicle body are positive results, as shown by lower impact severity parameters. The influence of wheel impacts with a post was not included in this first study. In a second study, a flared guardrail terminal was modelled and two vehicle models were modified to simulate an oblique impact situation. The purpose of these simulations was to improve the vehicle models, by refining their wheels and steering-suspension systems, for better prediction and reproduction of the vehicle behaviour in oblique collisions with guardrails. The refined front wheels and steering-suspension systems simulated better the impact behaviour of the vehicles for the wheel-post impacts. A vehicle model needs these refined systems to improve the analysis of oblique impacts with guardrails. With the aid of the computer simulation tool, a roadside feature can be crash analysed for vehicles under conditions that are not defined in a standard. Although only some of the simulations have been validated, due to high costs of crash tests, the vehicle models and guardrail models presented in this thesis can contribute to further numerical studies that simulate other roadside collisions.