Oxford pollution assessment project begins
24 June 2013 Last updated at 19:39 BST
Work has started on a project to assess vehicle emissions in Oxford.
The city council said while overall pollution had fallen there were some "hotspots", such as St Aldates, where bus numbers have increased.
Equipment is being used to shine an infrared beam across some roads in the city to detect the exact breakdown of exhaust gases.
BBC South Today's Emma Vardy spoke to Max Priestman from King's College London, which is carrying out the research, and councillor John Tanner.