This article solves the task to assess how much a car body construction influences on the parameters of passive safety in a rear impact. The task concerns the impact and, as a result, is highly nonlinear with large values of deformations, stresses, and accelerations. A finite element method based on software systems LS-DYNA, ANSYS, FEMAP, and others solves this task.

One of the most important stages of the work was to develop the finite element models (FEM) of the car as a whole, as well as the car seat with a dummy mounted in the car. Body of the Chiseler Grand Caravan car, which parameters are close to average ones, was used as an object of research.

The results of calculations and experiments allowed us to find that in assessing the passive safety of a car, taking into consideration the body design with a seat mounted in it, values of velocities, accelerations, and NIC criterion turned out to be lower than when calculating the seat with a dummy separately. The relative error (relative to the results of calculations in the "dangerous" impact of FEM seat of the highest level in accordance with EURO NCAP) was 32% for full acceleration and was 33% for NIC criterion.

It was found that in the calculations based on the FEM car, as a whole, the results are more accurate than when using the load operation conditions simulating energy absorption by the car body (20%).

This leads to the conclusion that the calculations based on the FEM car with the seat mounted in it gives the possibility to design a seat (with passive or active headrest) to ensure the best level of passive safety of this car.