4 ms·

> That doesn’t solve brake and tire particles. Regen braking means significantly less brake dust, especially at city speeds and with blended braking. > Althou

> That doesn’t solve brake and tire particles. Regen braking means significantly less brake dust, especially at city speeds and with blended braking. > Although…rail might solve those? Trains still have brakes. Some can regen brake but because they usually don’t have batteries they need the rail or overhead gantry to support inputs. But on a passenger-mile basis, I expect an electric train produces essentially no particulates compared to a car, even a light rail on tyres. I do not however have numbers.

jurip 2mo ago
I believe at least subways tend to have lousy air: https://engineering.nyu.edu/news/subway-air-pollution-disproportionately-impacts-new-york-citys-minority-and-low-income https://engineering.nyu.edu/news/subway-air-pollution-dispro... But I expect it's much better in open-air rail systems.
- masklinn 2mo ago
  I was thinking open-air yes, tunnels do indeed have major issue. With pollutant concentrations, road tunnels are the same (https://www.sciencedirect.com/science/article/abs/pii/S1361920920306659 https://www.sciencedirect.com/science/article/abs/pii/S13619...). For all that I did not care for them originally this is probably something full-height platform screen doors help with, assuming the trains themselves are also filtered that would keep the pollutants clear of drivers and users, although it does not exactly resolve the question of managing their presence in the tunnels themselves (and track / tunnel maintenance personnel should probably already be wearing respirators if not full breathing apparatus), and I could see things get pretty dire in case of breakdowns.
  - rsynnott 2mo ago
    Impossible to retrofit, of course, but what helps more are big tunnels. Modern ~9m diameter single tunnel systems are a lot better for this than old 3.5m diameter double tunnel systems.
Symbiote 2mo ago
The usual brake on a train that can't do regenerative breaking is a big grid of resistors to dump the energy as heat. It's much less wear and tear than friction brakes. https://en.wikipedia.org/wiki/Dynamic_braking https://en.wikipedia.org/wiki/Dynamic_braking
- rsynnott 2mo ago
  And diesel hydraulic trains (and some buses) usually use these: https://en.wikipedia.org/wiki/Retarder_(mechanical_engineering)#Hydraulic_retarder https://en.wikipedia.org/wiki/Retarder_(mechanical_engineeri...

jurip 2mo ago

I believe at least subways tend to have lousy air: https://engineering.nyu.edu/news/subway-air-pollution-disproportionately-impacts-new-york-citys-minority-and-low-income https://engineering.nyu.edu/news/subway-air-pollution-dispro... But I expect it's much better in open-air rail systems.

masklinn 2mo ago
I was thinking open-air yes, tunnels do indeed have major issue. With pollutant concentrations, road tunnels are the same (https://www.sciencedirect.com/science/article/abs/pii/S1361920920306659 https://www.sciencedirect.com/science/article/abs/pii/S13619...). For all that I did not care for them originally this is probably something full-height platform screen doors help with, assuming the trains themselves are also filtered that would keep the pollutants clear of drivers and users, although it does not exactly resolve the question of managing their presence in the tunnels themselves (and track / tunnel maintenance personnel should probably already be wearing respirators if not full breathing apparatus), and I could see things get pretty dire in case of breakdowns.
- rsynnott 2mo ago
  Impossible to retrofit, of course, but what helps more are big tunnels. Modern ~9m diameter single tunnel systems are a lot better for this than old 3.5m diameter double tunnel systems.

Symbiote 2mo ago

The usual brake on a train that can't do regenerative breaking is a big grid of resistors to dump the energy as heat. It's much less wear and tear than friction brakes. https://en.wikipedia.org/wiki/Dynamic_braking https://en.wikipedia.org/wiki/Dynamic_braking

rsynnott 2mo ago
And diesel hydraulic trains (and some buses) usually use these: https://en.wikipedia.org/wiki/Retarder_(mechanical_engineering)#Hydraulic_retarder https://en.wikipedia.org/wiki/Retarder_(mechanical_engineeri...