I take a lot of public transportation. Seems that subway trains often do this weird thing that I think of as a “reboot” where all the lights turn off, it goes silent, then starts back up again (all within about a second or two). It sometimes happens on electric buses too.
I’ve always assumed that it is the carriage losing contact with the electrical supply for a second. Are they designed to do this or is this a malfunction? Anything more you can tell me about it?
In the case of electric trains, it’s almost certainly due to momentary loss of contact with the third rail. This happens by design; third rails must have gaps to allow crossings and switches, and in the railroads (and subway) around here, often switch which side of the tracks they’re on. As long as the other cars in the train have contract, they can push/pull the one that’s momentarily out of contact. (In electric trains all cars, or in some cases every other car, has a motor.)
Cars should have emergency lighting that goes on when the main power cuts out. Some newer ones have battery power that can maintain the main lighting for a few seconds which is enough for most gaps.
I believe most subway trains have four “shoes” that get power from the third rail on each car - one at each corner - making power interruptions relatively unlikely.
As for rebooting, I have been on BART trains where the operator announced that the train needed a reboot, and it takes a couple minutes, much of which is spent sitting completely “dead in the water” with no lights (just a couple back-up lights over the doors) or ventilation.
I’ve also witnessed reboots on some of San Francisco’s newer electric trolley buses. They’ve got internal batteries, so they can drop the poles and drive a couple of blocks to get around accidents or construction. As described above, it’s everything shuts off, then the lights come on, the compressor starts up, and the destination / next stop display scrolls its version info and comes back on. At least these are pretty quick. IIRC, about 5-10 seconds.
This happens in the Washington Metro from time to time, when the trains are stopped waiting to enter a station. The lights don’t go off, but the ventilation shuts off, so I’m guessing there’s a bit of a charge still getting through to the train. But it’s definitely a “reset” of some kind.
The buses around here aren’t electric. But they’re so loaded down with gadgetry - touch pads and card readers and the like - that they occasionally require a reboot. The bus driver turns the entire bus off then on again.