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Washington DC To Return To Automatic Metro Trains
Bruce66423 (1678196) writes with news of interest to anyone with reason to ride mass transit in the U.S., specifically on the D.C. Metro system: After a crash some five years ago, automatic operation was abandoned. Now however replacement of 'faulty' modules means that moving the whole system on to automatic operation can happen. One quote is depressing: "And because trains regularly lurch to a halt a few feet short of where they should be at platforms, Metrorail riders have grown accustomed to hearing an announcement while they're waiting to board: 'Stand clear. Train moving forward.'" That never happens on the London underground with human operators? What's wrong with American drivers?
The Red Line crash was not computer-related. The signalling system for the Washington Metro is a classic electromechanical relay-based system. Just like the New York subways. The Red Line crash was caused by a failure of a track circuit for detecting trains, trackside equipment using an audio-frequency signal sent through the rails and shorted to the other rail by the train's wheels. All those components are pre-computer technology.
As with most railway systems, manual driving isn't enough to prevent collisions, because stopping distances are often longer than visual distances. That was the case here.
The Washington Metro had been sloppy about maintenance of trackside equipment. They do have a central computer system, and it logs what the relay-based signal systems are doing, although it can't override them. They had logs of previous failures, and should have fixed the problem.
First, as of 2010, DC was about 50% Black, 39% White, plus everybody else. Source: http://en.wikipedia.org/wiki/D.... As a (White) DC resident who moved back here a couple of years ago, one of the things I enjoy about the Metro is the casual, random, cheerful conversations I have with my fellow riders who happen to be Black. Second, I live in DC and ride Metro regularly. Occasionally there are annoying people (often Black), but very rarely threatening ones. Cell phone theft on the Metro is a danger here, like most places (and police don't seem to care anywhere). Third, Metro needs to better enforce its rules against food and drink (and smoking) in the system. In effect, Metro no longer enforces that rule so the cars can be a mess. I encountered a White guy smoking on a platform earlier this year and asked him to put it out. He blew me off, quite obnoxiously.
There were a bunch of cases of 8 car trains being stopped by the driver as if they were a 6 car train. This left one car of people in the tunnel. It was decided that instead of relying on the train driver to remember how long of a train they are driving, all drivers would be required to pull up to the end. (The right decision IMO.)
Hence, the acceleration and braking systems were optimized for automatic operation (as opposed to manual operation) and it is difficult for a human driver to control the train's movements precisely and smoothly.
I have a perspective on this that most probably don't, as I was a monorail driver at Disney World for a number of years. Contrary to what some might imagine, the current Bombardier Mark VI trains there are not attractions but are in fact full-up transit vehicles, and Bombardier continues to sell them as such (although with different bodies and newer electronics). If D.C.'s trains handle anything like ours did, I can understand why some of the drivers short-stop or otherwise have problems.
Our Mark VI trains were originally designed to accommodate automation as well, but I don't think this in itself really is a factor. More importantly, each train had its own "personality" and handled differently, and all of them would take between one and two seconds to respond after an input was commanded except for E-stops, which instantly opened the relay contactors and applied air to the friction brakes. One train might be ultra-responsive (relatively) to the throttle and have really tight brakes, which made it easy to drive and predict stopping distances with great accuracy. Others would act like your control inputs were more of a suggestion than a command, necessitating that you be looking a little ahead of where you actually wanted to be in order to stop where you were supposed to. We had some drivers that had difficulty dealing with that, and would often blow their stops by a couple of feet or so on a train with loose brakes, or would stop short if they were in a tighter train that didn't require so much anticipation of its behavior. I don't think I ever had a short stop, but did have trains "slide" on me a few times and missed the stop by just enough to have to back up a couple of inches to get lined up with the gates.
I would imagine transit trains everywhere exhibit similar unique peculiarities, and the only consistent way to deal with it is for the driver to be ultra-conservative, which can lead to the occasional short stop. It's not so much a problem for an automation system that can directly respond in milliseconds and isn't being moved between trains with wildly varying performance characteristics.
Please stand clear of the doors, por favor mantenganse alejado de las puertas
None of the Underground lines are driverless. The ones you list are GoA level 2 (i.e., opening/closing doors, starting the train, and emergencies are handled by the driver). Go look in the cab of any of them, they all have drivers!
Even the DLR is a GoA level 3 system, as the "attendant" handles door closing and emergency driving of the system.
The only GoA level 4 systems (which are truly driverless and can operate without any trained staff onboard) in the UK are the people movers at Heathrow T5, Gatwick, and Stansted.
The automatic system was fine for nearly 40 years. The upgrade process killed nine people and injured 80 and caused a safe system that ran reliably for nearly 40 years to run in "manual" mode for five years because of a maintenance error.
Several depositions from railroad workers who were tasked with upgrading Metro's nearly 40-year-old system mentioned a real problem. The signals were "bobbing." This happened because the older signal system was being replaced with a different vendor's technology in two phases with catastrophic results.
In phase one, the lineside signal cabinet equipment was replaced but the original track sensors were left. In other cases, it was reversed: the track sensors were replaced but the lineside signal cabinet equipment was original. In both cases the vendor was different and not totally compatible.
Naturally, as we would expect, the two different vendors' equipment was not interfacing perfectly. This caused signal "bobbing," where track occupancy would "bob" from red to green repeatedly. Trains would vanish from the system. Phantom trains would appear in the system.
This massive oversight reported in the depositions wasn't really taken seriously in the press nor by the accident investigation. From this point of view, the system failed due to incompatible equipment made to interface in order to save money and service disruptions. They didn't interface properly, and people died as a result. Nobody seems to care about what appears to be the real problem: incompatible vendors made to interface to save time and money.
But we now have faster trains with shorter headways that sometimes fail to stop at the correct spot in stations, so we have that going for us. At least the lineside cabinet equipment and track sensors are now from the same vendor, eliminating the problem that killed those people and put hundreds of thousands of others at risk for a couple of years until that deadly day in 2009.
Kriston