From a present perspective, environmental protection occupies a position of supreme importance, especially with regard to pollution levels due to motor vehicles. To reduce environmental pollution, the limits for pollutant emissions from cars have been gradually lowered over the past few decades in the type approval procedure and series inspections.
The emissions characteristics of vehicles in use are, however, crucial for the pollution level. To check the emission characteristics of vehicles in actual traffic and to monitor observance of the endurance requirements of the exhaust gas regulations, it is absolutely essential to introduce an informative and practical field inspection system on a legal basis. That means that emission measurements have to be carried out in the complete licensing test on the roller-type tester on the basis of the type approval procedure, and this to be done on vehicles with differing mileages from private customers.
In Europe there are statutory inspection procedures in the Netherlands and Sweden which are used to check the emission characteristics of vehicles in use with reference to the “recall-procedure” already in force in the USA.
It is only possible to a certain extent to transfer the results of the corresponding field inspection programmes of these countries to German conditions. On the one hand driving habits, especially on motorways, are different from those in the countries mentioned and, on the other, pollution reduction concepts are sometimes offered in Germany which are not exported abroad.
For the reasons mentioned and because of the lack of the relevant statutory regulations, it was thus necessary initially to implement a field inspection programme in the Federal Republic of Germany in the context of a research project in close contact with the Netherlands.
Measurements on more than 1300 vehicles in the Netherlands and Germany during the last years show that conspicuous type-specific features can be detected in “field inspections”. By the improvements made to the pollutant reduction concepts it is possible to lower the level of emissions from vehicles in use.