5 ms·

>And so this is why it’s tricky and this is why in your example of a bridge, if you widened the bridge but lots of people want to cross it, you’ll end up with a

>And so this is why it’s tricky and this is why in your example of a bridge, if you widened the bridge but lots of people want to cross it, you’ll end up with a wider bridge that’s exactly as congested as it is now. Widening the bridge does increase throughput; people who used to be unable to use the bridge are now doing so. There's a benefit there, it's just siphoned off from "reducing congestion" to "people are no longer forced to stay home rather than deal with congestion".

tonyedgecombe 9y ago
It might be a benefit economically but I'm not sure having more people sat in congestion is a good thing.
- ThrustVectoring 9y ago
  Facilitating more trips absolutely should be the goal of any transit system. Getting yourself from point A to point B provides you value - else why would you go? "More people sitting in congestion" just means that the facilitated trips are limited by capacity and density rather than geometric distance.
  - tonyedgecombe 9y ago
    Yet having more people sat in congestion is going to have a negative affect on societies overall wellbeing. The problem is we look at it from the perspective of the immediate economic benefit and ignore the costs of poorer health outcomes and increased environmental degredation.
    - ThrustVectoring 9y ago
      On further thought overnight, I agree with you more. There's a combined goal between zoning and transit to meet human needs, and obviating the need to make a trip on the zoning end is just as good as facilitating a trip on the transit end. The overall systems approach is better in total, too - there are tons of broad cross-cutting concerns here, and transit is one piece of a larger and more complex system.
deng 9y ago
His point is that if you make going by car more attractive by simply widening the bridge for everyone, people will switch from public transport to private cars. So his solution would be more "make a separate bus line on the bridge, so that they are more attractive to use than a private car".
- ant6n 9y ago
  Inducing demand is not just from mode-shift (towards cars in this case), but also from development. Take the example of a big city on a big island (e.g. Montreal), a larger bridge may encourage sprawl off-island rather than infill development on-island. A choke-point like a bridge isn't just a sort of barrier (geographic, social economic...), but also an opportunity to manage travel patterns and thus development.
asteli 9y ago
People don't generally give up and stay home, they find ways to go about their lives. Driving to downtown San Francisco is awful and congested, so people simply take the train (because it exists in a useful capacity). Widening that bridge has an opportunity cost. LA ramped up road infrastructure at the expense of useful public transit and urban densification, and it's a stressful and sickening experience to get around there.
- ghaff 9y ago
  I expect a lot of people do just stay home. If it’s a total PITA to go into a city after work people find other activities.
  - asteli 9y ago
    leisure trips account for a small fraction of the kind of trip we're talking about they APTA's study shows something like 15% of public transit trips are social or shopping/dining related[1]. i suspect the proportion would be similar (or lower) wrt road traffic. [1] American Public Transportation Association: http://www.apta.com/resources/statistics/Documents/transit_passenger_characteristics_text_5_29_2007.pdf http://www.apta.com/resources/statistics/Documents/transit_p...
djsumdog 9y ago
Wenover productions does a great video on how increasing traffic lanes makes traffic worse in every city. People who normally wouldn't drive, will now drive thinking they'll be less congestion. Atlanta had some major closures recently and the city migrated around the problem, people took different paths to work and more people decided to get on public transport. The fact is car lanes can never reach a fraction of the capacity of a train running at regular intervals. Even if you had nothing but self driving cars running bumper to bumper at 120kph and all filled to a capacity of 4.2 people, on a four lane road, you wouldn't even approach 8% of the capacity of a single rail line running at 2 minute intervals! Singapore's trains are automated. They're already self driving and run at <1.5min intervals during peak hours.
- deleted 9y ago
  [deleted]
- mseebach 9y ago
  There’s something wrong with your numbers. 120kph for two minutes is 1km, or 250 4-meter cars, bumper to bumper. Four lanes, 4.2 occupants, that’s 16,800 passengers per two minutes, which is a full order of magnitude more than a 12-carriage train packed with standing passengers[1] - and the people in the cars are all sitting down. 1: https://en.m.wikipedia.org/wiki/British_Rail_Class_700 https://en.m.wikipedia.org/wiki/British_Rail_Class_700
  - djsumdog 9y ago
    http://www.oregon.gov/ODOT/RPTD/RPTD%20Document%20Library/maximum-theoretical-person-capacity-24-hour-period.pdf http://www.oregon.gov/ODOT/RPTD/RPTD%20Document%20Library/ma...
    - schiffern 9y ago
      Ahh, that explains it. The paper assumes a sane minimum of 1.6 seconds/car (aka 2250 pcphpl), but 4 m spacing at 120 kph would be 0.12 seconds/car.

tonyedgecombe 9y ago

It might be a benefit economically but I'm not sure having more people sat in congestion is a good thing.

ThrustVectoring 9y ago
Facilitating more trips absolutely should be the goal of any transit system. Getting yourself from point A to point B provides you value - else why would you go? "More people sitting in congestion" just means that the facilitated trips are limited by capacity and density rather than geometric distance.
- tonyedgecombe 9y ago
  Yet having more people sat in congestion is going to have a negative affect on societies overall wellbeing. The problem is we look at it from the perspective of the immediate economic benefit and ignore the costs of poorer health outcomes and increased environmental degredation.
  - ThrustVectoring 9y ago
    On further thought overnight, I agree with you more. There's a combined goal between zoning and transit to meet human needs, and obviating the need to make a trip on the zoning end is just as good as facilitating a trip on the transit end. The overall systems approach is better in total, too - there are tons of broad cross-cutting concerns here, and transit is one piece of a larger and more complex system.

deng 9y ago

His point is that if you make going by car more attractive by simply widening the bridge for everyone, people will switch from public transport to private cars. So his solution would be more "make a separate bus line on the bridge, so that they are more attractive to use than a private car".

ant6n 9y ago
Inducing demand is not just from mode-shift (towards cars in this case), but also from development. Take the example of a big city on a big island (e.g. Montreal), a larger bridge may encourage sprawl off-island rather than infill development on-island. A choke-point like a bridge isn't just a sort of barrier (geographic, social economic...), but also an opportunity to manage travel patterns and thus development.

asteli 9y ago

People don't generally give up and stay home, they find ways to go about their lives. Driving to downtown San Francisco is awful and congested, so people simply take the train (because it exists in a useful capacity). Widening that bridge has an opportunity cost. LA ramped up road infrastructure at the expense of useful public transit and urban densification, and it's a stressful and sickening experience to get around there.

ghaff 9y ago
I expect a lot of people do just stay home. If it’s a total PITA to go into a city after work people find other activities.
- asteli 9y ago
  leisure trips account for a small fraction of the kind of trip we're talking about they APTA's study shows something like 15% of public transit trips are social or shopping/dining related[1]. i suspect the proportion would be similar (or lower) wrt road traffic. [1] American Public Transportation Association: http://www.apta.com/resources/statistics/Documents/transit_passenger_characteristics_text_5_29_2007.pdf http://www.apta.com/resources/statistics/Documents/transit_p...

djsumdog 9y ago

Wenover productions does a great video on how increasing traffic lanes makes traffic worse in every city. People who normally wouldn't drive, will now drive thinking they'll be less congestion. Atlanta had some major closures recently and the city migrated around the problem, people took different paths to work and more people decided to get on public transport. The fact is car lanes can never reach a fraction of the capacity of a train running at regular intervals. Even if you had nothing but self driving cars running bumper to bumper at 120kph and all filled to a capacity of 4.2 people, on a four lane road, you wouldn't even approach 8% of the capacity of a single rail line running at 2 minute intervals! Singapore's trains are automated. They're already self driving and run at <1.5min intervals during peak hours.

deleted 9y ago
[deleted]
mseebach 9y ago
There’s something wrong with your numbers. 120kph for two minutes is 1km, or 250 4-meter cars, bumper to bumper. Four lanes, 4.2 occupants, that’s 16,800 passengers per two minutes, which is a full order of magnitude more than a 12-carriage train packed with standing passengers[1] - and the people in the cars are all sitting down. 1: https://en.m.wikipedia.org/wiki/British_Rail_Class_700 https://en.m.wikipedia.org/wiki/British_Rail_Class_700
- djsumdog 9y ago
  http://www.oregon.gov/ODOT/RPTD/RPTD%20Document%20Library/maximum-theoretical-person-capacity-24-hour-period.pdf http://www.oregon.gov/ODOT/RPTD/RPTD%20Document%20Library/ma...
  - schiffern 9y ago
    Ahh, that explains it. The paper assumes a sane minimum of 1.6 seconds/car (aka 2250 pcphpl), but 4 m spacing at 120 kph would be 0.12 seconds/car.