Timeline for How could the level crossing at the end of Back to the Future 3 know that the locomotive would arrive?

6 events

when toggle format	what		by	license	comment
Jun 16, 2020 at 9:31	history	edited	CommunityBot		Commonmark migration
Jul 28, 2015 at 20:25	comment	added	Wad Cheber		@IanAuld - Most rails are 1/2 of a circuit, so in most cases, 1 out of every 2 rails has a mild current running through it. Just enough to be detected, not enough to kill anyone.
Jul 28, 2015 at 20:11	history	edited	Wad Cheber	CC BY-SA 3.0	added 112 characters in body
Jul 28, 2015 at 16:10	comment	added	Scott Whitlock		@IanAuld - actually, that makes no difference. If all you want to do is check continuity (if the tracks are connected to each other through a train) then you could just measure resistance between the rails. You are using electricity to do this, but it's not high enough voltage that you'd notice if you touched it. I'm not saying this is how it works, but as an electrical engineer, I assure you that Wad's answer is reasonable.
Jul 28, 2015 at 15:59	comment	added	kylieCatt		I'm no expert on trains but having spent a fair amount of my childhood playing on train tracks in NYC (completely unelectrocuted) I can tell you that the tracks are absolutely not electrified. There is a "third rail" that is electrified but that has a cover on it and the train has a little arm that reaches out to make contact.
Jul 28, 2015 at 3:32	history	answered	Wad Cheber	CC BY-SA 3.0