A17.1 has for a long time required 2 lamps in the car interior for illumination, and in the 2016 and 2019 codes allowed for a automatic switching between the two with an alarm if one went out, then resorted back to the 2 lamps required language again. In our area Otis has been replacing two florescent units with a single LED unit. I know in the 90s some of the manufactures were using flourecent fixtures with two ballast in them, does anyone know if Otis's LED fixtures had dual power supplies to meet the code? They look like standard home depot lamps to me.