The cab air conditioning with roof-mounted condenser system provided greatly increased driver comfort in hot weather conditions while also reducing wind noise in the cab. In fact, under some conditions on side roads, drivers were said to open the door and ride on the running board or steps to keep cool prior to the advent of cab air conditioning. Red Dot claims to have designed the first integrated heater-a/c system in a heavy-duty vehicle. It was for Kenworth, around 1970. Before that and for most of the 1970s rooftop air conditioners were sold as factory and dealer installed options. These systems were more like aftermarket designs than the highly integrated cab air of today. That’s why the condenser was on the roof, preventing it from capitalizing on the power of the engine-driven fan.