Summary In Europe pedestrian safety is a significant issue and has been researched in working groups and research projects. Among others this has resulted in European legislation related to pedestrian protection provided by passenger cars fronts. However, in the Netherlands more bicyclists than pedestrians get killed in road traffic, which is a main concern of the Fietsersbond. Although it is currently investigated in APROSYS Sub Project 3 if pedestrians and cyclists have to be seen as separate groups of vulnerable road users, it is unknown if pedestrian protection legislation also has a significant benefit for cyclists. Hence, the Fietsersbond has requested TNO to perform an inventory study with the aim to:
- make an investigation in pedal cyclist to car accidents using simple vehicle,
bicycle and cyclist models, and
- indicate possible measures to vehicles for improved bicyclist safety.
The study has been performed using numerical simulations in the MADYMO simulation software. First multibody models were developed of passenger cars (small family, mid-sized family and SUV) and a bicycle. The models were used together with a released average male human model (as cyclist) in a baseline simulation representing a typical cyclist-vehicle impact where the cyclist is laterally impacted by a mid-sized passenger car with an initial velocity of 50 km/h. In addition a simulation study was performed varying both impact conditions and vehicle parameters.
The analysis of the vehicle-bicycle impact event was done using the global cyclist kinematics and impact velocities for the relevant body parts. In addition, the head, chest, pelvis and lower leg accelerations and the HIC value were used as indication of the injury. Due to the conceptual nature and the limited level of validation of the models, the results were used to study global trends, instead of absolute, precise values.
In the baseline simulation the most severe loading was found to be on the lower leg and the head, which is in line with the findings from an earlier study that the head and the legs are the most frequently injured body regions for cyclist and pedestrians. In the variation study it was found that:
- a reduction in the impact velocity reduced the injury levels estimated by the models. A reduction in impact velocity could for instance be obtained by infrastructural measures.
- the shape had a large influence on the kinematics of the cyclist. The small vehicle model with a shorter and steeper bonnet resulted in a better load distribution over the body and reduced head loading. The SUV model, with its high bonnet leading edge, caused a direct load on the pelvis and upper legs, which could result in severe injuries in the pelvic region.
- a reduced stiffness of the rigid parts in the windscreen area resulted in a significant reduction of head injuries estimated by the models.
- the velocity and the impact position influenced the possibility of having a ‘second impact’ with the ground and its severity. This impact is not taken into account in this study.
As the current study was an inventory study, it is recommended for future research to:
- validate the models more specific for cyclist-vehicle impact loading which will lead to an improved predictive capability. Furthermore, although it is realized that only limited data might be available, accident data could be analyzed to derive the relevant parameters and ranges in bicycle to car accidents.
- study the front-end and bonnet stiffness in more detail. In the current study these components were found to have only a limited influence, which is partly because only the (initial) deformation force level was varied and not the stiffness and position of underlying rigid components. Further research could indicate the effects of e.g. varying the available deformation space and could lead to an optimized design towards injury minimization.
- investigate the difference between pedestrian-vehicle and bicyclist-vehicle impacts as this could indicate if the measures for pedestrians could also have a significant benefit forcyclists or if additional measures are needed.
Link to movies of the computer simulaties at www.fietsersbond.nl.
(verkennende studie naar de invloed van autofronten op het het letsel voor fietsers).