Subways are dusty because they use mechanical brakes that produce metal dust particles.
For $50 per carriage, dust collecting sponges, fans or filters could be fitted, but train companies don't care. By doing anything about the dust they might be opening themselves up to lawsuits claiming they didn't do enough about a risk they knew about... There are also political issues - often the train company bought the trains 50 years ago and will pay extortionate prices to the original manufacturer for any modifications, and if they make modifications themselves the manufacturer will drop all support.
Many modern trains are starting to have electric braking, and that produces far less dust.
I think he's referring to the horrifically unmaintained and archaic state of the world's older subways, like NYC and the London Underground. Besides the expense, NYC is absurdly behind on modern train timing systems, which causes very loose scheduling and frequent delays. There's also the general squalor and lack of maintenance of the platforms. London's tunnels are so full of iron dust and other particulates that a half hour in them literally turns your mucus black, and the lack of a cooling system has caused the ambient temperature to rise ~30 degrees since their construction with no sign of stopping. They also screech loudly enough to cause permanent hearing damage.
These systems could be modern and effective, but instead they're disintegrating in place. That's the problem.
The system is too essential for a stop-the-world overhaul, but so far gone, that only a stop-the-world overhaul can part the clouds.
Without a hard flush of antiquated mission critical infrastructure, millions of turbulent eddies and vortices will ensure that the system is always afflicted by parasitic equipment and debris.
NYC Subway is really hard-core about train stops. There's a trip cock on every subway car, near the right front wheel, and it works by directly operating an air valve to the brakes. The train stop lever alongside the track is raised by a big spring and lowered electrically, and the signaling system senses when it's physically up, ready to trip. Only then can the preceding train stop lower. There are always several train stops up between trains. A signaling failure or power cut will raise the train stops.
"The central principle of signal placement and engineering is that the control lengths of the signals be so designed such that when a train running at the highest possible speed under the worst weather conditions, with any semblance of functional brakes, is tripped, it will come to a halt before encountering the other train or obstruction that is causing the signal to be red."
Some signals have timers, for speed control. Go through a block too fast, and the signal ahead won't clear. Then the train stop will stop the train. This is common in downhill sections and ahead of curves.
Resetting a trip cock in NYC requires getting out of the cab and climbing down to the tracks. This is Not Fun.
Chicago has self-resetting trip cocks, which resulted in an accident in 2013.[1] A train parked in a service yard had a water leak into the control cables, which caused the train to move, slowly. The train hit a train stop, the brakes were applied, and the train stopped. But
the trip cock reset, and the train started again. This happened five times at five different train stops. Workers noticed, but were not able to stop the train. This continued until the train hit an occupied but stopped train just outside the yard.
Many people have written many articles about the NYC subway recently. Because the trains run 24/7, they cannot renovate lines and install advanced train control. Because of the terrible train control, they put simplistic speed limits on trains. Because of all the slow trains the number of passengers per train increases, resulting in more platform delays and medical emergencies.
This reminds me of the trouble they've had upgrading Air Traffic Control systems.
I grew up in Manhattan and rode the subway constantly. I remember sometimes taking the front car, looking out the window and wondering what the odds were of a collision. Then a friend explained how the red light control system made it physically impossible for one train to crash into another.
Ha! Glad I didn't know the truth back then, I might have developed a phobia about using the subway.
Its worse than you think. I can't find the source right now but IIRC the NYC subway signals still run on the vacuum tube system designed in the early 1900s. At the time it was a massive technical accomplishment. Every small arrangement of vacuum tubes is like a purpose built computer for signaling a specific section of track with speeds and spacing pre-calculated. It successfully put an end to high profile accidents caused by human error. Today you could do the same thing with a micro-controller for almost no money.
As mentioned in the article, this technique is used in New York City's subways, too. I have a lot of problems with the MTA, but they're still stellar by American standards.
The problem with doors in New York in particular is that not all generations of rolling stock have doors in the same location. Unlike MTRC, where one line has its own rolling stock and there is no interoperation between different lines, many services, each with different door positions, can utilize the same platforms. And basically the only way to have a door configuration compatible with all rolling stock is to not install any doors at all.
You could replace the rolling stock, but all of it is in good operating condition, and the last of the oldest cars with non-compatible doors would be retired in the 2030s.
Air conditioning is also a huge challenge; traditionally, New York's subway has been cooled using the piston effect of trains, with frequent grates open to the surface to draw in air. With air conditioning those large, frequent openings are now a curse.
reply