4 ms·

I'm hoping the aircon filters will start clearing the filthiness of the tube air. Something tells me they'll have to change them more often then think. Once yo

I'm hoping the aircon filters will start clearing the filthiness of the tube air. Something tells me they'll have to change them more often then think. Once you see it, you can't unsee it. There's this dark mist in the London underground, I find it very visible on the northern line, around elephant and castle. Just standing at one extreme of a platform and trying to look at the farthest part of the station, you'll realise everything is "foggy" by lack of a better term. One hour there would turn my snot black.

morkalork 3y ago
There was a study on the TTC subway and they discovered the air quality was 10x worse than above ground and on par with Beijing. The accumulation of dusty linty particles on the walls has a cute name too "tunnel fur". I remember seeing workers going into the tunnels wearing N99 masks after that report was released.
- glompers 3y ago
  I always like the (grease?) smell in Montréal Metro stations but never thought about it in terms of particulate matter concentrations.
  - morkalork 3y ago
    Unfortunately the only smell I can associate with the Montréal metro is piss
  - VK538FY 3y ago
    I understood that the Montreal metro trains used wood breaks and peanut oil. Hard to say if that makes the same mess, but the rubber tires surely leave something. Also, the new rames may use different breaking technology.
    - lbourdages 3y ago
      They initially used different brakes, but they reverted to the good old peanut oil brakes because they had issues of some sort with dust. I'm struggling to find a source that tells the reason, but here you can see they chose wooden brakes. https://www.stm.info/sites/all/modules/custom/stm_import/imported_files/a-%20FicheMPM-10maquette_12.pdf https://www.stm.info/sites/all/modules/custom/stm_import/imp...
rjmunro 3y ago
One thing the article doesn't mention is that the trains are more efficient because they use regenerative braking, rather than friction brakes. The friction brakes cause a lot of the heat and dust in the underground. By eliminating this heat, they are able to use that heat budget to run air conditioners on the trains and they still make less heat overall. As a side effect, the dust should be reduced too (and probably a bit of the maintenance)
- rob74 3y ago
  There is actually an intermediate step between "friction brakes" and "regenerative braking" - electric trains can use the engines to brake, but the current produced is then fed to resistors, which dissipate it as heat, rather than used to charge a battery or to feed it back into the power supply line - https://en.wikipedia.org/wiki/Dynamic_braking#Rheostatic_braking https://en.wikipedia.org/wiki/Dynamic_braking#Rheostatic_bra.... So the friction brakes are actually only used when maximum braking is required - and these will also be needed with regenerative braking. Using regenerative instead of rheostatic braking will however lower the amount of heat produced I guess...
  - cpncrunch 3y ago
    The 1973 trains already used rheostatic braking. The new ones use regenerative braking. https://www.modernrailways.com/article/revolution-piccadilly-line#:~:text=This%20is%20because%20the%20new,this%20is%20some%20way%20off https://www.modernrailways.com/article/revolution-piccadilly.... http://www.trainweb.org/tubeprune/73%20tube%20stock.htm http://www.trainweb.org/tubeprune/73%20tube%20stock.htm
Cthulhu_ 3y ago
I can understand that cooling a tunnel network like that is difficult, but surely filtering particles from the air is a solvable problem? Movable air filters on the platforms, etc.
- kilotaras 3y ago
  Step 1 is to measure and declare a problem. To the best of my knowledge there's no systematic measuring of air pollution on the stations. Same with loudness which on some (old) lines is way past safe.
  - Symbiote 3y ago
    Air quality is measured: https://tfl.gov.uk/corporate/about-tfl/improving-air-quality-on-the-tube https://tfl.gov.uk/corporate/about-tfl/improving-air-quality...
    - kilotaras 3y ago
      I can get real time air quality index above ground on multitude of places. The most up-to date information on the tube I could found was this report[0], that only covered a number of stations. Even then, the information provided is not great, e.g. for Highbury & Islington: > The results for particulate matter were between <0.02 and 2.16 mg/m3 for PM2.5. Results cover the range from 4x of WHO recommended limit (5 μg/m3, i.e. 0.005 mg/m3) to 432x. [0] https://content.tfl.gov.uk/dust-monitoring-lu-stations.pdf https://content.tfl.gov.uk/dust-monitoring-lu-stations.pdf
  - addandsubtract 3y ago
    Visiting London, there were two things I didn't understand about the underground. 1. Why is it _so_ hot in the tube? I can understand when the metro in Madrid gets hot, but London?! 2. How many people living in London, and taking the underground regularly, have hearing problems? How can a train be that loud and still be allowed to operate?! I've never experienced a train as loud as on the Victoria line.
jwestbury 3y ago
There's another fun aspect of this -- combined with the lubrication, it leaves escalator rails near some lines absolutely filthy. I've got a pair of trousers permanently stained because I put my hand on the rail while walking down the escalator to the Northern Line at Embankment, didn't notice it had become absolutely covered in black gunk, and then touched my thigh. This seems to be a problem almost exclusively on deep tube line escalators, in my experience.

morkalork 3y ago

There was a study on the TTC subway and they discovered the air quality was 10x worse than above ground and on par with Beijing. The accumulation of dusty linty particles on the walls has a cute name too "tunnel fur". I remember seeing workers going into the tunnels wearing N99 masks after that report was released.

glompers 3y ago
I always like the (grease?) smell in Montréal Metro stations but never thought about it in terms of particulate matter concentrations.
- morkalork 3y ago
  Unfortunately the only smell I can associate with the Montréal metro is piss
- VK538FY 3y ago
  I understood that the Montreal metro trains used wood breaks and peanut oil. Hard to say if that makes the same mess, but the rubber tires surely leave something. Also, the new rames may use different breaking technology.
  - lbourdages 3y ago
    They initially used different brakes, but they reverted to the good old peanut oil brakes because they had issues of some sort with dust. I'm struggling to find a source that tells the reason, but here you can see they chose wooden brakes. https://www.stm.info/sites/all/modules/custom/stm_import/imported_files/a-%20FicheMPM-10maquette_12.pdf https://www.stm.info/sites/all/modules/custom/stm_import/imp...

rjmunro 3y ago

One thing the article doesn't mention is that the trains are more efficient because they use regenerative braking, rather than friction brakes. The friction brakes cause a lot of the heat and dust in the underground. By eliminating this heat, they are able to use that heat budget to run air conditioners on the trains and they still make less heat overall. As a side effect, the dust should be reduced too (and probably a bit of the maintenance)

rob74 3y ago
There is actually an intermediate step between "friction brakes" and "regenerative braking" - electric trains can use the engines to brake, but the current produced is then fed to resistors, which dissipate it as heat, rather than used to charge a battery or to feed it back into the power supply line - https://en.wikipedia.org/wiki/Dynamic_braking#Rheostatic_braking https://en.wikipedia.org/wiki/Dynamic_braking#Rheostatic_bra.... So the friction brakes are actually only used when maximum braking is required - and these will also be needed with regenerative braking. Using regenerative instead of rheostatic braking will however lower the amount of heat produced I guess...
- cpncrunch 3y ago
  The 1973 trains already used rheostatic braking. The new ones use regenerative braking. https://www.modernrailways.com/article/revolution-piccadilly-line#:~:text=This%20is%20because%20the%20new,this%20is%20some%20way%20off https://www.modernrailways.com/article/revolution-piccadilly.... http://www.trainweb.org/tubeprune/73%20tube%20stock.htm http://www.trainweb.org/tubeprune/73%20tube%20stock.htm

Cthulhu_ 3y ago

I can understand that cooling a tunnel network like that is difficult, but surely filtering particles from the air is a solvable problem? Movable air filters on the platforms, etc.

kilotaras 3y ago
Step 1 is to measure and declare a problem. To the best of my knowledge there's no systematic measuring of air pollution on the stations. Same with loudness which on some (old) lines is way past safe.
- Symbiote 3y ago
  Air quality is measured: https://tfl.gov.uk/corporate/about-tfl/improving-air-quality-on-the-tube https://tfl.gov.uk/corporate/about-tfl/improving-air-quality...
  - kilotaras 3y ago
    I can get real time air quality index above ground on multitude of places. The most up-to date information on the tube I could found was this report[0], that only covered a number of stations. Even then, the information provided is not great, e.g. for Highbury & Islington: > The results for particulate matter were between <0.02 and 2.16 mg/m3 for PM2.5. Results cover the range from 4x of WHO recommended limit (5 μg/m3, i.e. 0.005 mg/m3) to 432x. [0] https://content.tfl.gov.uk/dust-monitoring-lu-stations.pdf https://content.tfl.gov.uk/dust-monitoring-lu-stations.pdf
- addandsubtract 3y ago
  Visiting London, there were two things I didn't understand about the underground. 1. Why is it _so_ hot in the tube? I can understand when the metro in Madrid gets hot, but London?! 2. How many people living in London, and taking the underground regularly, have hearing problems? How can a train be that loud and still be allowed to operate?! I've never experienced a train as loud as on the Victoria line.

jwestbury 3y ago

There's another fun aspect of this -- combined with the lubrication, it leaves escalator rails near some lines absolutely filthy. I've got a pair of trousers permanently stained because I put my hand on the rail while walking down the escalator to the Northern Line at Embankment, didn't notice it had become absolutely covered in black gunk, and then touched my thigh. This seems to be a problem almost exclusively on deep tube line escalators, in my experience.