Estimation of Fuel Consumption and CO ₂ Emissions of Car Travel in Transportation Planning: The Lazio Region Case Study

In transportation planning studies, equilibrium traffic flows and speeds are commonly post-processed to provide estimates of fuel consumption and CO₂ emissions. CO₂ emissions are tightly linked to fuel consumption. Two methods for this estimation are compared in the paper, depending on whether the fuel consumption factor (per vehicle-km travelled) of different vehicle classes is independent (first method) or dependent (second method) on the average speed of the individual links of the road network. Fuel consumption and emission factors are from the COPERT database by the European Environment Agency. The analysis restricts to cars. The results of the Lazio region case study (Italy) are indicative that the magnitude of the bias that affect the first method compared with the more detailed second method can be as high as 20%.