**7. Conclusions**

The reduction of exhaust emissions requires a continuous search for new solutions in both engine design and methods of engine testing. A main factor stimulating this development is the exhaust emission legislation in which they are in progress. The advancement of exhaust emission measurement techniques provides new possibilities of engine and vehicle testing particularly under actual conditions of operation (RDE). One may suppose that this method will become prevalent and will gain significance. The aim of the legislators and manufacturers should be the acknowledgment of the RDE measurements as one of the main methods of homologation testing works. The aim of introducing such changes should be completed as soon as possible and the enforceability of the implemented legislation should be global.
