Environmental aspects of intersection design is highly neglected in the planning and construction process. The motor vehicle in the road network infrastructure has been alleged to be ‘the root of the evil’ and sole reason for the detrimental air pollution and other environmental disturbances. But it is also necessary to pay attention to the infrastructural design aspects when looking for ways of reducing the traffic-related exhaust pollution in the ambient air. It must be possible to find an optimal intersection design for the environment. This paper deals mainly with the methodological aspects and the possibilities of obtaining necessary data for studies within this field and specifically the application of comparative environmental studies of air polluting emissions. Also, this paper contains a case study regarding the changing of a traffic signal to a roundabout. Speed, acceleration and deceleration profiles are created with the help of field measurements of driving patterns. Data is collected from video pictures taken from a helicopter or from a high mast, and the data evaluation process is done by the help of an especially developed computer program. Conclusions regarding the differences in environmental aspects (pollution levels) are then drawn on the basis of the obtained data from before and after micro-studies of the traffic flow. The paper also includes a before-and-after case study where a traffic signal intersection was changed to a roundabout. The study gave very positive performance results for the roundabout compared with the traffic signal intersection, and as a typical result it was found that the average driving speed through the intersection in one direction could be increased from 20 km/h to 40 km/h, and as a result of this, the HC-emission per vehicle could be decreased from ∼2.5 g/km to ∼1.6 g/km.