Intensity of motor trucks operation versus vehicles’ age, in several categories of engine cubic capacity

Changes in the vehicle operation process, which take place with vehicle’s age, have been analysed on the grounds of data collected for over 3 000 motor trucks of more than 3 500 kg gross vehicle mass (GVM), being now in use in Poland. The analysis has covered a 20-year vehicle operation period (referred to as “service life planned”); the distance travelled by a vehicle during this period has been called “target mileage” (expressed in kilometres). As a measure of the intensity of vehicle operation, the “monthly mileage” has been adopted. The monthly mileage values specified in the article strongly depend on the category of engine cubic capacity. Some important characteristics of the mileage growth process, noticed in the recent years along with an intensive development of the road transport, have been presented. The vehicle mileage growth process has been shown for four categories of engine cubic capacity, on the grounds of regression lines based on a polynomial model. The vehicles with engines of more than 10 000 cm3 capacity reach more than 1/3 (i.e. 34.7-36.6%) of their target mileage for the first 60 months of operation, while covering only 2-5.3% of this target mileage during the last two years of their 20-year service life planned. During the first 5 years, the intensity of operation of vehicles belonging to this engine capacity category is four to five times as high as that determined for the last 5 years of the 20-year vehicle operation period under analysis. Calculations carried out have shown that the dataset under analysis includes vehicle categories where 90% of the target mileage is reached as early as after 69-70% of the service life planned. This shows that motor vehicles having been used for a short time predominate in the road transport of goods in Poland and that there is an interrelation between the rates of changes in the vehicle operation intensity and the engine capacity.