“The results of an emissions test carried out in connection with vehicle inspection are only indicative, since the test only measures a few gas components,” Senior Researcher Santtu Mikkonen from the Department of Applied Physics at the University of Eastern Finland says.
“Measuring the number of fine particles is now being introduced to the inspection protocol, but it is not done in a real driving situation, either.”
“In our ongoing study, we are analysing car emissions in real driving situations under winter conditions.”
The joint study by the University of Eastern Finland and Tampere University involves a mobile laboratory, fitted in a van, which has an internationally unique collection of sensitive devices that measure particle concentrations and their chemical composition, as well as gases.
“Normally, car emissions always get mixed with outdoor air. With these devices, we can analyse exhaust gas samples for particulate and gas emissions, including soot and carbon dioxide,” says Mikkonen.
“With a mass spectrometer, it is possible to study the size and composition of particles, among other things.”
“The study will also take into account how emissions age and transform in a few days’ time due to, for example, sunlight. This is relevant to the results in the longer term,” Postdoctoral Researcher Miska Olin from Tampere University adds.
In a set of measurements carried out in Kuopio this February, the researchers used their mobile laboratory to chase six cars, one at a time, from a five-metre “safety distance”. The 16-kilometre route included accelerations, braking and idle time in “traffic lights”, similar to a normal driving situation. The maximum speed was 80 kilometres per hour. Exhaust gases were sucked in from the air for analysis in the van.
The cars followed were different diesel and petrol cars, the researchers' own cars and rental ones – however, much newer than cars typically seen on Finland’s streets.