Air starters were somewhat common on Over - the - Road tractors and trucks ( class 7 & 8 ) for many years. With the new, more powerful ( and higher compression ) diesel engines coming into service in the late 1960's & early 1970's, the maintenance and expense of electric starters was becoming excessive for some LTL carriers. Cold weather damage to batteries was also a factor. Consolidated Freightways, and their Conway baby brothers, used air starters on their " Heavy Duty " Line tractors up through the late 1990's, while Viking Freight System used air starters on all their tractors for many years. A side benefit of air starters was the weight savings from not having to carry 4 heavy batteries for a 24 volt starter system. Of course there was the need for a separate starter compressed air bottle on the truck somewhere, plumbed independant of the brake air system. Charging a depleted air starter system was rather simple, as another tractor was spotted alongside, and the red trailer supply line was hooked to a gladhand on the starter bottle. Push in the red brake button, pump it up, and it's Happy Trails !!! Not any more difficult than hooking up jumper cables.