What criteria/basis have been used for the locations of Clean Air Zone signage? Who chose the locations of the signs?

Signs have been located according to Department for Transport design principles and national guidance, including the Traffic Signs Manual and Traffic Signs Regulations and General Directions.

TfGM have worked with Local Authority officers to determine where signage that is required to be sited in each Local Authority should be placed. The locations were formally agreed by each Authority in July 2021.