The Prague city demonstration campaign of the Horizon 2020 EU project CARES was a huge success. The campaign was running from 5th-23rd Sept. 2022. During this period three remote emission sensing techniques were measuring the emissions of vehicles in and around Prague to detect high-emitting vehicles. Besides cross-road remote sensing and point sampling, plume chasing was employed. During the last years this technique has been further developed within the CARES project with a leading role of the Institute of Environmental Physics and its high-tech spin-off Airyx GmbH. Plume chasing is now easily applicable by authorities. This was tested during the Prague CARES campaign with truck measurements on the highway and police enforcement. About 1000 heavy-duty vehicles were measured by Plume Chasing. Over 11% showed very high NOx emissions. A fraction of those vehicles were pulled over for further inspections by the police. Several defects and manipulations could be found. Further information about the plume chasing method and the Prague campaign can be found on the Airyx and CARES website.