Abstract
The results described in this paper represent a part of the measurements which are carried out in the region of Cologne in order to express the exhaust emission present in the air. It may be seen that the determination of traffic in density built-up urban areas is insufficient to give evidence as to the extent of emission of noxious substances which are to be expected. Therefore, it is also necessary to carry out thorough investigations of the traffic conditions and the specific emissions from the motor vehicles, after which reliable quantitative results for emissions due to vehicles can be obtained, so that it will be able to introduce measures for improving the present condition.