NYC Subway Riders See 'Exceptionally High' Air Pollution
bloomberg.com
bloomberg.com
https://www.nyserda.ny.gov/-/media/Project/Nyserda/Files/Pub...
And those don’t rub. There will surely be some emissions from the wheels rolling imperfectly on the track, but, perhaps naively, that should be small. I wonder whether NYC trains also have friction brakes that they use for the last bit of stopping. If so, perhaps improved control algorithms or improved motor drivers could avoid using them until the train is fully stopped.
There’s also another possible effect: trains produce high air velocities, and they could stir up small particles that have settled in the ground. A serious effort to clean up the tracks and stations could reduce these particles.
The researchers found that the rubbing of metal wheels and brakes on the rails releases metal particles, which appear in particular concentrations as the trains arrive at a station.
“We noticed that when a train arrives at the station, the concentration in the air shoots up, and about 15-20 seconds after it leaves, the concentration slowly comes down,” said Ghandehari. “This implies that it is the stuff that’s at the bottom of the tunnel that gets churned up and deteriorates the air.”
Most modern EVs can come to a near stop using regenerative braking without applying mechanical brakes at all. Some motor controller software could surely bring it to a complete stop with minimal or no hardware changes. (If you find a safe place with no obstacles, you can generally stop a car, EV or otherwise, by driving slowly forward, shifting to reverse, and stepping gently on the accelerator. In a car with a conventional engine, this involve friction internal to the clutch or torque converter. In an EV, it’s the motor applying torque opposite to its direction of rotation.)
A subway train quite similar to an EV.