Incorrect pressure in tyres are often one of the causes of accidents. However, there is no research on the effect of lowered pressure on accident history. This concerns also new types of tyres: run-flat and low-profile. In the experiments the influence of advanced technology on adhesion coefficient and vehicle dynamics were tested. Statistically significant differences were observed between tyres of correct and incorrect pressure. It was proved that lowered pressure decreases motion stability, with practically no effect on braking parameters. This fact was confirmed, by chance, during one of the tests, when the driver lost control over the vehicle with a completely flat tyre.