The EU sets the path towards zero CO2 emissions for new passenger cars in the future. Reaching net zero, there will be a period of co-existence between conventional vehicles and zero-emission vehicles. Engineers and policymakers should proceed to direct approaches, taking steps to reduce road pollution by reassessing the road design. Roundabouts enforce speed variations. Depending on the driving behaviour, can result in high pollutant emissions. The objective of this paper is to understand the factors and the parameters that contribute to high pollutant emissions. The trajectories of 260 vehicles at six multilane roundabouts were analyzed. Video image processing techniques allowed the extraction of accurate kinematic characteristics gathered on the field using a UAV. The VSP methodology was applied to calculate carbon dioxide. The results of the quantitative analysis demonstrate strong relationships with road geometry. Road designers should consider the aspect of the environment and choose geometric variables wisely.