The subject of the MEDETOX project is to measure the toxicity of diesel emissions in real urban traffic, focusing on the situation on the Prague ring road. Standard test cycles in laboratory conditions do not accurately represent vehicle emissions in real traffic. Therefore, the project will develop a prototype of a mobile testing device that will measure the basic components of emissions in real traffic and sample emissions for subsequent biological or toxicological tests. The health risk assessment of emissions must be based primarily on the interaction of emissions with model biological systems and not only on the chemical analysis of their components. The project's main objective is to use existing methods for toxicity analysis of complex mixtures to assess engine emissions in real traffic. Applying its results should lead to improving the European Union legislation on the regulation of motor vehicle emissions.