4 ms·

This analysis ignores people who use only the train and tube or just the tube. If you hinder the tube to try and improve traffic what will happen is traffic wil

This analysis ignores people who use only the train and tube or just the tube. If you hinder the tube to try and improve traffic what will happen is traffic will eventually increase where you have made improvements (the bottlenecks referred to in the article) and the tube service has still been degraded. The failure of the analysis is to assume that car drivers should be a consideration (perhaps that is due to the US bias toward car travel over public transport). Really we need to be improving public transport such as the tube so much that car driving is disincentivising as much as possible and public transport is incentivised as much as possible.

notahacker 11y ago
I'm inclined to question whether the study authors have ever been to London, never mind examined actual passenger throughput data. Most tube stations have far too little parking in the vicinity to create a "bottleneck" by encouraging overuse of personal transport, and "bottlenecks" with bus services are far more sensibly resolved by increasing the frequency of bus services at peak times than slowing trains down.
raverbashing 11y ago
I think you're right on your first paragraph But the consideration about traffic is not only about cars but people that do Bus->Tube and vice-versa
- notahacker 11y ago
  I can't see any part of the study that distinguishes between the congestion effects caused by cars and buses (or indeed walking and cycling, which the naive speed-optimisation specification of the study assumes away altogether) This is pretty critical to some of the conclusions: a subway line creates congestion at the ends of subway lines rather than them becoming a logical nexus for bus routes.
alvin0 11y ago
True that article ignores passengers using only tubes or trains. But I think the article suggests global congestion may be improved by slowing down certain parts of a system. Even considering only people using just the tube, the tube station can switch only a finite number of passengers in and out of tubes. If a system has two bottlenecks, improving the narrower bottleneck will result global improvement only until that bottleneck is no longer the narrowest. It is possible that increasing tube throughput would increase arrival rates at the destination stations. And if we consider congestion as nonlinear to number of passengers arriving at the station, then this might decrease the throughput at that station (beyond some threshold arrival rate); (I think this transition is similar to a phase change). That would mean the second bottleneck would effectively becoming slightly narrower in capacity, and thus the global throughput decreases. The trick would be to improve the narrowest bottleneck; but not too much, that it would cause such phase transitions at other points in the network. At which point, we need to start looking at other bottlenecks.

notahacker 11y ago

I'm inclined to question whether the study authors have ever been to London, never mind examined actual passenger throughput data. Most tube stations have far too little parking in the vicinity to create a "bottleneck" by encouraging overuse of personal transport, and "bottlenecks" with bus services are far more sensibly resolved by increasing the frequency of bus services at peak times than slowing trains down.

raverbashing 11y ago

I think you're right on your first paragraph But the consideration about traffic is not only about cars but people that do Bus->Tube and vice-versa

notahacker 11y ago
I can't see any part of the study that distinguishes between the congestion effects caused by cars and buses (or indeed walking and cycling, which the naive speed-optimisation specification of the study assumes away altogether) This is pretty critical to some of the conclusions: a subway line creates congestion at the ends of subway lines rather than them becoming a logical nexus for bus routes.

alvin0 11y ago

True that article ignores passengers using only tubes or trains. But I think the article suggests global congestion may be improved by slowing down certain parts of a system. Even considering only people using just the tube, the tube station can switch only a finite number of passengers in and out of tubes. If a system has two bottlenecks, improving the narrower bottleneck will result global improvement only until that bottleneck is no longer the narrowest. It is possible that increasing tube throughput would increase arrival rates at the destination stations. And if we consider congestion as nonlinear to number of passengers arriving at the station, then this might decrease the throughput at that station (beyond some threshold arrival rate); (I think this transition is similar to a phase change). That would mean the second bottleneck would effectively becoming slightly narrower in capacity, and thus the global throughput decreases. The trick would be to improve the narrowest bottleneck; but not too much, that it would cause such phase transitions at other points in the network. At which point, we need to start looking at other bottlenecks.