Due to the importance of the pollution of cars, buses and tracks from Diesel engines, the “Centro Sviluppo Materiali” of Rome has studied a particular device for the electrostatic precipitation and the combustion of the particulate from exhaust gases (MEA). After the study and the construction of the device, many tests controlled by the Ministry of Transport both on engines of 2500 cc and 9600 cc have been undertaken.The reliability tests were carried out on a urban and extra-urban buses.The results of tests can be summarized as follows: a) the back pressure values obtained by using MEA are always lower than a standard silencer, while High Voltage Power Supply does not affect the other electronics on the vehicle; b) (tests made upon a 2500 cc engine), the decreasing capacity of the Bosch smoke has been lower at high revolutions per minute. Anyway reduction average value of the smoke has been about 60%. The particulate decrease in weight ( 0.06 g/km ) has been well under the limits indicated by the standards (0.14 g/km); c) ( tests made upon KHD and DAF engine ), as regards the particulate reduction in smoke per cent the results obtained confirm all already reported in the experimentation carried out on the engine 2500 cc. Smoke was reduced from 2.77 Bosch index to 0.12 in 13 mode tests of a DAF Diesel engine. As a consequence the Italian Ministry of Transport authorized the installation of the CSM device on the motor vehicles transporting both people ( up to 5 t, Sector M) and goods (up to 12 t, Sector N ).