Active bonnet system is usually used in higher price range models of cars. Its application in small cars is exceptional. Therefore, the aim of this paper is to use numerical simulations for investigating this case. That is, to evaluate possible benefit of active bonnet system for a small car. We use a novel approach in developing a simplified model of a car bonnet. Its surface is segmented to form an MBS model with hundreds of rigid bodies. Each of them is connected via translational joint to a base body. Local stiffness of each joint is validated using a headform impactor corresponding to the EuroNCAP mapping. Hence, the structures beneath the bonnet are taken into account. The model of the bonnet is embedded in a whole model of a small car in a simulation of a real accident. VIRTHUMAN model is scaled in height, weight and age to represent exactly the pedestrian involved. Injury risk predicted by simulation is in correlation with data from real accident. Developed model of a small car is then used to assess the benefit of an active bonnet system. VIRTHUMAN models of a 13-year-old boy (150 cm, 40 kg) and a 18-year-old male (178 cm, 72 kg) are chosen to represent the pedestrians. Lateral impact at 45 km/h is considered. In this case, FE model of the bonnet is considered with deployed position given by prescribed displacement. Various initial positions of pedestrians with respect to vehicle considering both deployed and undeployed system lead to the total number of 72 simulations. The effect of active bonnet system is evaluated in terms of pedestrian injury risk.