0ur transport correspondent katy austin has been speaking to businesses and residents in birmingham and bradford about the impact clean air zones are having. signs like these have become a common signs like these have become a common sight. we ve just entered birmingham s clean air zone watch has been birmingham s clean air zone watch has been in birmingham s clean air zone watch has been in operation forjust over two years has been in operation forjust over two years. it s has been in operation for ust over two ears. , ., has been in operation for ust over two ears. fl ., ., has been in operation for ust over two years. two years. it s one of seven that have sprung two years. it s one of seven that have sprung up two years. it s one of seven that have sprung up in two years. it s one of seven that have sprung up in cities - two years. it s one of seven that have sprung up in cities around | have sprung up in cities around england over the past few years. here, driv