Gap in the third rail

I was watching Saturday Night Fever. When Tony is in the subway going to visit his girl, the lights go out in his car for about a second (and the emergency lights come on). Three seconds later, the lights go out in the next car in the train.

Back in the 60's, this same thing would happen about 1/4 mile before entering Kendall (from either direction). I assume both of these were caused by a gap in the 3rd rail that exceeded the distance between the two pickup shoes at each end of each car.

What was the point of having such a large gap in the 3rd rail. I don't believe that it happenes any more and I can't recall it happeneing whenever I'm in other subway systems. Did they shorten the gap or do the cars have batteries to keep the lights on for short periods?

I remember when I first noticed the end of the third rail at Harvard... back when subways were still (and they still are I guess) somewhat new to me. I thought it was a mistake or something that broke.

From what I've gathered the newer trains have battery backup to prevent power loss during cutouts.

One reason for having a gap is to separate power sections. The older incandescent lit cars only had battery backup for emergency lighting.

typesix wrote:One reason for having a gap is to separate power sections. The older incandescent lit cars only had battery backup for emergency lighting.

May I assume that the gaps still exist but now there are batteries for all lighting, not just emergency lighting?

This raises my curiosity... How long before the regular lights shut off and how long before the emergency lights shut off.

I was on a MetroNorth train a few years ago when the train stopped due to power problems. IIRC, it was about 5 minutes before the regular lights quit. We were stuck for over an hour but it was daylight. I don't know if the emergency lights were still on.

I've had lights go off and then on again on the Red Line, so these gaps must still exist.

Another reason why the old RedBirds had the lights go out approaching stations was because the 3rd rail is usually between the both tracks (outbound & inbound), except for in stations where the platform is in the center, in which case the third rail is on the opposite side, away from the platform.