A road freight vehicle fleet represents the basic means for the work of a transport company, for which reason it is the most important element of its business doing. Its work directly influences the volume of the income from and costs of business operations of a transport company. The correct sizing and management of the road freight vehicle fleet is of essential significance to the cost-effectiveness of the enterprise and the satisfaction of demands for transporting. The defining of a road freight vehicle fleet and the selection of the vehicles that it will consist of are a complex problem, which should be approached from several aspects.     

In the paper, a fuzzy model for determining the justifiability of investing in the renewal of a truck road freight vehicle fleet and the assessment of the time period needed for return on such investment is presented. The forecasts of the expected volume of transport, i.e. income from transport, have been made on the routes with constant flows of freight for the realistic pessimistic and optimistic variants for the recommended period of the exploitation of a vehicle.