The characteristics of heat-absorbing glass for passenger cars are described with regard to climate perception and visibility of the driver, both of which are important aspects of active safety. Such modern types of glass reduce the transparency to heat and at the same time maximise light in the visible spectrum. To be in a position to quantify the advantages and disadvantages in the visible spectrum as regards transparency, dazzling, reflectance and diffused light, practical road-test runs were carried out on the same public roads under different conditions in light and climatic environmental. The tests comprised physico-technical, physical and psychological data with regard to driving behaviour of and strain on the drivers. The results confirm the predominance of advantages of heat-absorbing glass and provide, indications as to optimising the side and rear windows by increasing the degree of heat-absorbing.