Southern Pacific road switcher diesels often had elaborate lighting clusters front and rear, with a large red Mars Light for emergency signaling, and often two pairs of sealed-beam headlamps, one on top of the cab and the other below the Mars Light on the nose. Starting in the 1970s SP had cab air conditioning on all new locomotives and the unit is visible on the cab roof. Southern Pacific placed large snowplows on the pilots of their road switchers for the heavy snowfall on Donner Pass. Many Southern Pacific road switchers had a Nathan-AirChime model P3 or P5 air horn with chords distinct to Southern Pacific locomotives in the western states.