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Trains that decouple and recouple

I've often wondered why, when you have an electric train line that has a terminus as the main destination, you can't give everybody an express train.

To do this, imagine for the commute home, a 5 car train starts downtown. It leaves and expresses a few stops down the line. (A local car leaves after to handle the stops close to downtown.) When it gets to point one, with sufficient warnings and many safeguards, it decouples, and the rear car brakes to stop at the first of its stations.

Passengers get off (and on as well, see below) and the car, which has its own power coupler, takes off to drop folks off at the next few stations. The main train releases another car after that which handles the next few stations.

This has been thought of before, but next the hard part, something needing more modern technology. After the drop-off car has completed its local run, it would attempt to rejoin the next express train, allowing local passengers who got on it to get on an express, then move to the car that will eventually decouple to go to their stop. With the right timing this could go on all day.

Not that this is easy...A live docking is a complex thing. Today we might be able to pull it off by combining two different computerized systems with failsafes, and a human overseer. The train cars would have to have giant springs on their couplers to allow the impact to be absorbed. The motors and brakes of both units would need to be in fully computerized sync, and any failure would cause the rear to brake and the front to accelerate (if possible) to avoid collision, though it should be possible to deal with a moderate collision with the springs.

Of course you need special doors at front and back of the cars to allow passengers to flow, big enough for a wheelchair to get through which makes it more complex.

Of course, if all you want is a one-way trip with almost everybody leaving the downtown station and getting off at their own statiions you can do this much more simply, without any coupling or decoupling. Just have N independent cars, and the first car to leave expresses towards the last stations on the line, the next car to the ones before that and so on. The cars can be spaced a fat distance. I presume they don't do this because this travel pattern isn't that common.

Another alternative is to have the express simply stop every N stations and join with the local car that left the last express while stopped at the station. If scheduling finds it easier, a car could be picked up by the main train in either direction, though passengers picked up by the local car would need to get off to get on the next express when it comes through.

This does require that an express go through fairly often. If doing the local hops takes the car 10 extra minutes, an express could run every 15 minutes or even every 20, since the 10 minute wait would be justified by being able to catch a nice fast express.


Holy Moly!

I sent this to Bob Metcalfe, the inventor of the internet at least where he hides-out in Maine, and he poo-pooed it, as been thought abt be4. Soo. You are the first I've seen who thought abt it enough to write it. Bene.
I call it chaincar, and like your inventor of the net being accting, everybody pipes in half, is kind of a Buckminster Fuller geodesic dome, linkage. BUT, my substantiation is irrelevant to the mechanisms, for what cannot man do mechanically..., rather that the man hours lost, or GAINED, if one could address activities of work or pleasure by not keeping you eye on the creeping car in front of you. The gain is staggering. The creator? mobile phones. cells! And finally, the link? Visuality, moving visuals unleashes the mind.

Trackback from TheBlog: I make that the figure for what Bill Gates has earned (and this figure is increasing) on average in the last 25 years. As Brad points out, that makes it just about feasible that he can pick up a......

Brad, actually, there was an academic paper with this scheme that was rejected at the main natl transp. conf this year. No offense to you - the academic author had some problems with the scheme.

Meanwhile personal rapid transit gets the same job done differently. PRT is an elevated monorail system with many three-person, driverless, electric vehicles. It is ideally suited for short "feeder/distributor", shuttle, and "circulation" operations at train stations, airports, office parks, and shopping centers. PRT provides non-stop, no-wait, 30 mph service.

Vehicles travel above ground on 16' elevated "guideway." Stations are located near building entrances. Many stations are situated along the route to minimize walking once the trip ends. Vehicles travel non-stop to their destination along the main guideway at 30 mph, speeding at twice the average speed of autos on congested streets below. Stations are NOT located on the main guideway; instead, stations are located on separate station guideway that branches from the main guideway. Thus, stations are described as "off-line," meaning "not on the main line."

PRT combines concepts from monorail (Disneyland), automated people movers (SeaTac Airport), roller coasters, and automated highway systems (California Governor Schwarzenegger's GM OnStar van drives itself in the science fiction movie The Sixth Day).

Passengers travel alone or with people of their choosing. Vehicle weight minimization greatly reduces the size of the elevated guideway and supporting columns, dramatically reducing construction cost and right of way acquisition. Vehicles flow along the guideway almost like data packets on the Internet, anticipating demand so that wait time is eliminated. In addition to improving commute alternatives, the PRT system eliminates mid-day stranding caused by traditional carpooling/transit, by providing efficient transit to adjoining shops and restaurants.

PRT system capacity is roughly 4,000 person trips per hour per PRT "loop." Systems may have many loops, providing more capacity.

For a nice animation of PRT visualized at Microsoft campus, check out

I wrote a paper on PRT in my high school geography class (that's the 70s) so I know about it And while the tech for it continues to improve, it's hard to say when cities will actually buy it. It's not likely to succeed any more than other forms of transit in the sprawls of California, it could do well where other transit does well.

I have wondered if they couldn't make a PRT hybrid, based on a standard (and thus cheap) car chassis, with regular tires for the road and magnetic drive for the PRT track. That would get people more into it.

In the 1930 and 40's Britain has such working, known as slip coaches,

the rear coach could detatched whilst the train is in motion, it had no power but a brake that could be applied to bring it to stand in a station.

the whole thing however was eventually dropped as too costly too impractical on a modern high speed network.

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