Complex sentence: When Traffic Departments were first set up Police officers were issued with long white coats, the first Hi Visibility coats were day-glo orange but since the late 1970s the preference has been for day-glo Saffron Yellow.
Split into simpler sentences: When traffic departments were first set up the officers were issued with long white coats. The first hi-visibility coats were day-glo orange, but since the late 1970s the preference has been for day-glo saffron yellow.