Chasing real-world driving emissions
Heidelberg researchers are following vehicles through city streets, sampling their exhaust plumes to get a better perspective on emissions.
The Volkswagen scandal underlined the inadequacy of standard lab tests, which do not reflect the exhausts produced when driving in the real world.
But the University of Heidelberg team is now getting more reliable data by tracking behind cars and buses to "sniff" their tailpipe gases.
Dr Denis Pöhler from Heidelberg's Institute of Environmental Physics explained the issues to our correspondent Jonathan Amos.
19 Apr 2016