The influence of the probability density of the average speed on the probability density of the specific road exhaust emissions has been analyzed in the paper. The characteristics of the exhaust emissions from internal combustion engines warmed up to normal operating temperature have been examined. The research has been carried out for characteristics of the exhaust emissions from internal combustion engines of passenger vehicles. The research has been carried out for two kinds of functions in the form courses of average speed: of constant and normal distribution. The Monte Carlo Method has been used in the research. The probability density of the specific road exhaust emissions has been estimated. The zero–dimensional characteristics: the median, the kurtosis and the skewness coefficient, have been examined. A significant regularity of the displacement of the probability density towards smaller values in relation to the average speed probability density has been ascertained.