The purpose of this paper is that of demonstrating the influence of the driver's stress on the vehicle safety.

This analysis concerns through one aspect of the active safety because of the possibility to reduce accidents when the capabilities of the drivers will be kept at the best level.

Some anatomic region of the body have been taken into consideration and analysed in terms of uncorrect posture which will produce stress.

The regions analysed are the head including cervical spine, trunk and pelvis, upper and lower limbs.

After a brief description of the function of these elements of the body the aspects of the posture related to the distribution of the mechanical loads, both static and dynamic, have been analyzed.

The uncorrect posture will modify the distribution of such a loads and consequentely will produce stress.

Even though a deep analysis of biomechanism of the regions of the body taken into consideration would involve more time, we have tried to put down the guide lines and the concepts for evaluating the relationship between load and posture in order to extablish the way to follow for understanding better this important aspect of the safety.

Therfore the mathematical aspects and formulas involved have been kept to the minimum possible avoiding complication in the presentation but without reducing the understanding of the problems.

As a conclusion of this study we can say that a sound choice of the geometry of the seat, of the steering, brake and clutch is fundamental for reducing stress and improving the safety of the car.