Bi-directional signalling, primarily in LA

I've heard that the LA subway and light rail both offer dual-direction service on one of their tracks if the other is out of service, and so can avoid bustitution most of the time. Is the the case anywhere else in North America?
Do LA subway trains have end doors?

As a matter of regular operations? I have no idea.

I can tell you that I was riding the wrong side of the tracks in Chicago this weekend. They were doing repairs, which frequently leads to wrong-way running. That said, they do seem to try to limit that sort of operation to the weekend nights.

As far as I know, Atlanta's MARTA is fully bidirectional. They regularly disrupt the weekend schedule and take one side of one segment of track out of service for "single tracking." Trains merely crossover at a crossover or pocket track on one side of the disruption, then cross back over at the other end. Other than the delays through the switch and the necessary scheduling adjustments, the trains aren't significantly affected.

WMATA is notorious for single tracking on the DC Metro.

Even if the signalling is not set up for it, wrong-railing happens on pretty much any system due to equipment moves, service disruptions, etc.

No matter what kind of signaling is installed - having a track out of service for maintenance or any other reason puts a serious crimp in operations, even weekend operations. A track out of service of normal daily operations would cripple the system.

Depends on the density of the service. New York is basically limited to the midnight hours; a place with longer headways and lots of interlocked crossovers would have less of a problem. Every system has to do maintenance sometime--we all know what happens eventually if they neglect it. And if an emergency occurs, the existence of reverse signaling can mean the difference between service disruptions and no service at all: "seek alternate transportation."

mmi16 wrote:No matter what kind of signaling is installed - having a track out of service for maintenance or any other reason puts a serious crimp in operations, even weekend operations. A track out of service of normal daily operations would cripple the system.

But I've heard that LA doesn't need to bustitute as often. Just how often do trains pass each other on double track sections, particularly on weekends? If it doesn't last long when it happens, surely not.

ExCon90 wrote:Depends on the density of the service. New York is basically limited to the midnight hours; a place with longer headways and lots of interlocked crossovers would have less of a problem. Every system has to do maintenance sometime--we all know what happens eventually if they neglect it. And if an emergency occurs, the existence of reverse signaling can mean the difference between service disruptions and no service at all: "seek alternate transportation."

Apparetly, I've read that there are some triple track sections in New York, for peak direction express services.

There are, but the center track does not have platforms at local stations. One expedient used in New York is to have trains in one direction use the center track, omitting intermediate stations, with boarding passengers directed to take a local in the prevailing direction to the first express station, reversing direction there, and alighting passengers to ride to the next express station beyond their destination and take a local back. A nuisance, but better than changing to a bus.