Here is a photo of an auto accident in 1958, which took place on US101 (Pacific Coast Highway) in Los Angeles. As you will see; LAPD responded two traffic enforcement cars. They are the 58 and 56? Chevys. The traffic officers are the ones wearing the white hats. The Dodge is a CHP cruiser. I'm not sure which ambulance service the two tone rig belonged to; however it is interesting that it does not have a beacon or siren on the roof. I can see what appears to be a siren behind the grill.
http://digitallibrary.usc.edu/search/controller/view/examiner-m15085.html?x=1260567150920
http://digitallibrary.usc.edu/search/controller/view/examiner-m15085.html?x=1260567150920