I hadn't known that Police cars have thermal marking on their roofs for easy identification from their with no necessary intervention.
Just rather interesting and opens up other possibilities too especially as I think in a few years time we will see an increase in thermal image cameras in a many areas of our lives including in our cars. Most interesting.
Produced by Police Scientific Development Branch - Thermal Roof Markings for Police Vehicles by Alan Brooke Publication 43/04
For the Home Office
http://www.psdb.gov.ukDocument located
here. There are strict copyright notices so I have not quoted it.