The article evaluates the ecological and economic indicators of selected types of locomotives used on railway lines in Poland. Rail vehicles are characterized by lower emissivity and energy consumption in comparison to the majority of currently used means of transport, which translates into higher ecological efficiency of the transport system in the scale of the whole country. The share of rail transport in overall transport in Poland and its development are limited by several aspects related to the costs of purchase and exploitation of vehicles, infrastructure and the availability of new technologies. The article presents the results of measurements carried out on 15 units of the ST44 locomotive with varying degrees of technical wear, and thus representing a wide range of technical states of this type of vehicles operated on Polish railroads. The tests have shown the impact of the degree of technical wear of a diesel locomotive both on the level of exhaust emissions as well as the fuel consumption value.