The paper presents the results of the study on the sensitivity of the national annual emission of pollutants from passenger cars to their average velocity under the following traffic conditions: urban, rural, and on motorways and expressways. The study was carried out in accordance with the methodology used in the COPERT 4 software. The effect of traffic speed within cumulated categories of passenger cars on the national emission of pollutants was analyzed. The national annual pollutant emission of pollutants was found to be substantially affected by the average car velocity, this effect being largely differentiated due to the character of road traffic. The type of the dependence of the national annual pollutant emission on the average velocity is similar for all substances, especially under traffic conditions in rural areas as well as on highways and expressways. A distinct minimum of the national pollutant emission was found at a velocity of about 70 km/h under rural conditions.