In this paper, the influences of road and traffic conditions on fuel consumption and fuel costs of conventional diesel, parallel hybrid and stoichiometric CNG buses in intercity bus service are analysed. Calculation of fuel consumption and fuel costs for these three different bus technologies was conducted for road network of the Republic of Serbia. Three scenarios were considered. The first scenario includes bus traffic volume carried out on the road network in 2014. The other two scenarios are characterized by the decrease i.e. increase of traffic volume by 20% with unchanged state of road infrastructure in comparison to the year 2014. Obtained results show that in intercity bus service the greatest influence on the fuel consumption of buses has operating speed of the bus, followed by terrain type on which buses operate. The impact of other factors (international roughness index, fluctuation of traffic volume by 20% and correction factors of fuel consumption) is less pronounced. In various operating conditions the fuel cost savings per 100 km of CNG buses compared to diesel buses are in the range of €8.84-12.16. These cost saving for hybrid buses compared to diesel buses are in the range of €3.33-7.27.

In this paper, the calculation of exhaust emission costs originating from aircraft and road vehicles in the base year 2017 and in the forecasting year 2032, in the Republic of Serbia, was carried out. The presented methodology includes a number of influential factors for air transport (airport capacity, number of operations, aircraft type, relevant engine, range) and for road transport (changing of traffic volumes, design and operating speeds, the quality of the pavement structure, type of terrain and category of road sections, dependence of exhaust emission from changes in vehicle speed). It was found that in the current operating conditions, the dominant costs in the total exhaust emission costs are the costs of nitrogen oxides (61%) in road transport, whilst carbon dioxide costs are dominant in air transport (52%). In the future, carbon dioxide costs will have a share of over 80% in the road transport sector and over 58% in the air transport sector in total exhaust emission costs. The average exhaust emission costs per one aircraft operation (international flights) will range from 141 to 145€. In road transport, the average exhaust emission costs at 100 km in 2032 will range from 1.8 to 2.2€.

The paper gives special attention on long distance passenger transport and specific emissions related to different transport modes, particularly road and air transport sector. The goal of this research is creation and selection of appropriate methodology for modelling the cost estimation of GHG emissions in road and air transport sector for Republic of Serbia as well as the application of the methodology regarding to detailed calculation by transport mode and sub modes. Input data for road transport sector refer to the 2013 and include road and traffic conditions on the road network. Input data for air transport sector are related to the 2014 and international airport ‘Nikola Tesla’ Belgrade as the main hub point with the highest recorded number of aircraft operations in the Western Balkan countries. The obtained results reveal that, due to realized transport volume, diesel cars have the largest share of the costs of GreenHouse Gas (GHG) emissions within the passenger long distance road transport. Cost estimates of CO2 emissions in the air transport sector shows that A319 aircraft type have the major share in total costs. The reasons are twofold: first, a high level of Landing and Take-Off (LTO) emission factor for CO2 and second, largest number of LTO cycles.