Abstract Road freight transportation is the most common mode of long-distance timber transportation. This study assesses the environmental impacts of the larger and heavier vehicles on emission efficiency for 76 t vehicles using the synchronized calculation method. The method took account of two factors: load mass and the migration of loads to heavier vehicles. The method was successfully tested to calculate emission efficiency after the short-term adaptation process. Calculations were made for four mass limits (60, 64, 68 and 76 t) year after the mass limits were raised. Based on Enterprise Resource Planning data, efficiency of CO 2 emissions (measured in relation to trip) increased 15.8% for 76 t vehicles. Respectively, CO 2 emissions reduced 6.2% to 42.8 g/tkm. The results show that increase in maximum vehicle mass yields cleaner wood procurement chain in pulp production process. This study confirms that the synchronized calculation method can be used in real-world transport systems and local wood supply chains to determine and solve emission efficiencies of larger and heavier vehicle combinations.