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> When it comes to roads, why is increasing capacity to resolve the capacity problem always automatically dismissed? There's a large body of evidence [0][1] in

> When it comes to roads, why is increasing capacity to resolve the capacity problem always automatically dismissed? There's a large body of evidence [0][1] indicating that adding road capacity does not alleviate congestion. In the short run, one tends to see immediate rises in traffic on the new infrastructure. Over a longer period, the amount of traffic utilizing new infrastructure increases until all added capacity is being consumed. This is known as induced demand [2]. Congestion pricing [3] is a more economically viable manner of reducing congestion on shared infrastructure, but it comes with its own set of concerns [4]. [0] https://www.citylab.com/transportation/2015/11/californias-dot-admits-that-more-roads-mean-more-traffic/415245/ https://www.citylab.com/transportation/2015/11/californias-d... [1] https://www.wired.com/2014/06/wuwt-traffic-induced-demand/ https://www.wired.com/2014/06/wuwt-traffic-induced-demand/ [2] https://en.wikipedia.org/wiki/Induced_demand https://en.wikipedia.org/wiki/Induced_demand [3] https://en.wikipedia.org/wiki/Congestion_pricing https://en.wikipedia.org/wiki/Congestion_pricing [4] https://www.nytimes.com/2018/04/09/nyregion/congestion-pricing-manhattan-albany-fail.html https://www.nytimes.com/2018/04/09/nyregion/congestion-prici...

AmericanChopper 8y ago
All this means is that capacity is so far behind demand that current spending doesn't come close to establishing a reasonable equilibrium. Which is what you'd expect after decades of major population growth, accompanied by infrastructure neglect.
- nickles 8y ago
  > All this means is that capacity is so far behind demand that current spending doesn't come close to establishing a reasonable equilibrium. I'd hesitate to specify that certain equilibria are reasonable while others are not. Building more roads to reduce congestion does not achieve that goal, in part because of the latent demand you describe (see [0] "Effect in transportation systems"). Ultimately, if your goal is to decrease time spent traveling, you will see more benefit from alternative policies. Such policies may include: * increasing cost of using the roads (e.g. congestion pricing) * constructing alternate, denser forms of public infrastructure (e.g. subways) * increasing the density of passengers in vehicles (buses, carpooling, etc.) * funding technological advances that increase the density of vehicles utilizing the road (e.g. self driving cars) [0] https://en.wikipedia.org/wiki/Induced_demand https://en.wikipedia.org/wiki/Induced_demand
  - AmericanChopper 8y ago
    There’s lots of ways to approach defining a ‘reasonable’ equilibrium. You could set a target for average time spent communing, but to address a problem like the one described in the article, you’d just need to build enough freeways to ensure that using a freeway is on average faster than winding through suburban streets. You could do this by decreasing the efficiency of the non-freeway roads, or increasing the cost of using the roads, which both only ‘solve’ the problem by reducing general quality of life (especially for poorer people, who might just get even poorer if they can’t commute affordably). Or you can increase road capacity to keep up with population growth, and invest in alternative transport that people actually want to use. That means no cycle lanes or buses, because people really don’t want to use them (buses are only really efficient for short trips, if you have to change buses to get to work then it ends up taking so long you may as well just be inefficiently sitting in the comfort of your own car).
    - kalleboo 8y ago
      > Or you can increase road capacity to keep up with population growth This doesn't work because in a city you'll eventually you end up with more roads and parking lots than buildings. US cities were built like this, and the more road capacity you build, the more sprawl you get (everything is further apart), which increases how much people have to drive which increases the traffic... It's an evil spiral of congestion.
- danmaz74 8y ago
  In dense city environments, it's just physically impossible to build enough capacity to meet the potential demand for car rides at peak hours without congestions. You may hate public transportation, but than is the only solution that demonstrably work, together with scooters and yes, even bikes where geography and weather make them viable.
- hcurtiss 8y ago
  Exactly. I live in a small town. We have no traffic jams, and never have. I believe that proves it’s possible to build sufficient infrastructure to eliminate or reduce traffic jams. It’s just that most large cities elect not to.
  - wjnqx 8y ago
    I don't think the cost of that is justified in large cities. LA already dedicates more land area to automobile infrastructure than anything else, and the region is still plagued by traffic jams. At the end of the day, a single rail line can bring an amount of people in and out a city equivalent to multiple lanes of traffic. That's a lesson Americans forgot after 1945 for whatever reason, and now we have to re-learn it from the rest of the world now that we've hit the limits of car-oriented development.
  - mantas 8y ago
    Dense large cities are economically unviable if you try to accommodate car traffic. The tale of them being cheaper is true only if you give up large living spaces and personal transport.
  - dmoy 8y ago
    Or perhaps for a large enough city, you can't build enough roads, because you'd need like >70% of all area for roads and parking. The scaling doesn't work. For another similar example, think of how much percentsge space you need in a 2 story building devoted to elevators (almost none) vs a 200 story building (a significant percentage of the middle core of the building is nothing but elevators). Take that and scale it even worse, and you have roughly the small town vs big city traffic issue.
  - deleted 8y ago
    [deleted]
  - quotemstr 8y ago
    Yep. Induced demand is a nuanced concept that's been perverted by a certain community of activists into "science says you can't build enough roads so let's not build any!!!!1111". The truth is that you can, in fact, build enough roads to reduce congestion. It may be too expensive. The road land use fraction may be too high. There may be political problems. All of these factors have to be taken into account before deciding to build more roads. Nevertheless, it is physically possible to build enough roads, and anyone who doesn't acknowledge this basic reality isn't having a serious conversation.
arkh 8y ago
But: isn't it a good thing? More traffic is what those roads are for. More traffic means more activity. Focusing only on the capacity / congestion couple is myopic. If you really want 0 traffic just remove all roads: not sure the side effects will be as easily dismissed.
closeparen 8y ago
The goal of transportation infrastructure is to move people to their destinations quickly. It turns out that adding road capacity moves more people, rather than moving the same people more quickly, but that's still a success case. If we should reject road expansion because it fails to decrease travel times, then we should certainly reject a shift towards public transit, which actively makes them much worse. "Congestion" is a non-problem. You get no points for "solving congestion" by kicking everyone off the road. It's quite likely that a highly congested road is still delivering better end-to-end travel times and user experience than a realistic bus system. "Solving congestion" is great for you if you can afford the congestion charge, but it's not clear why a democratic society should let the rich kick the poor off the roads for their personal convenience. Really the only angle under which it's a coherent goal is reducing carbon emissions, but then you don't even need to talk about induced demand - it's sort of obvious that more road capacity means more driving.
- pasabagi 8y ago
  Why does public transit increase travel times? Good public transport is far more efficient than car-driving, for the simple fact that you can fit fifty people on a bus, and five hundred on a train. This massively alleviates congestion, is vastly more mechanically efficient, and massively simplifies planning. In a city with bicycle lanes, bikes are a lot faster than cars for short trips, and they require far less infrastructure - since bike lanes are about a third of the width of a road, and they require no dedicated parking space. Not to mention the fact that bikes are far cheaper to own and operate. I can understand having a sentimental attachment to cars - but in practical terms, they're a ridiculous solution to the problem of mass transit.
  - closeparen 8y ago
    >Why does public transit increase travel times? Because we don't all share an origin, destination, and schedule. Public transit can be extremely effective for the parts of the journey that it covers, but the extreme ineffectiveness of walking the other parts can cancel all that out. You have to completely rethink density and development patterns to get to a point where most origins and destinations are near stations. That would take decades even if we wanted to do it, and SB827 was just defeated in California. Then you have to run trains frequently enough that schedules don't matter. That's expensive as hell and the necessary capital projects take decades. And even if you do them, they might deteriorate and regress later if you don't keep up with the maintenance (see: New York). When I lived in Berkeley, BART covered 90% of my commute distance, station to station, in 25 minutes. My actual end-to-end commute time was over an hour, basically a wash compared to taking an Uber over the Bay Bridge at rush hour. Bicycling to my local station got it down to maybe 50. 25 minutes is an entire commute the average American. Being just 1.5 miles away from a station doubled that. Public transit has a wickedly hard problem to solve - even 90% coverage is still next to useless.

AmericanChopper 8y ago

All this means is that capacity is so far behind demand that current spending doesn't come close to establishing a reasonable equilibrium. Which is what you'd expect after decades of major population growth, accompanied by infrastructure neglect.

nickles 8y ago
> All this means is that capacity is so far behind demand that current spending doesn't come close to establishing a reasonable equilibrium. I'd hesitate to specify that certain equilibria are reasonable while others are not. Building more roads to reduce congestion does not achieve that goal, in part because of the latent demand you describe (see [0] "Effect in transportation systems"). Ultimately, if your goal is to decrease time spent traveling, you will see more benefit from alternative policies. Such policies may include: * increasing cost of using the roads (e.g. congestion pricing) * constructing alternate, denser forms of public infrastructure (e.g. subways) * increasing the density of passengers in vehicles (buses, carpooling, etc.) * funding technological advances that increase the density of vehicles utilizing the road (e.g. self driving cars) [0] https://en.wikipedia.org/wiki/Induced_demand https://en.wikipedia.org/wiki/Induced_demand
- AmericanChopper 8y ago
  There’s lots of ways to approach defining a ‘reasonable’ equilibrium. You could set a target for average time spent communing, but to address a problem like the one described in the article, you’d just need to build enough freeways to ensure that using a freeway is on average faster than winding through suburban streets. You could do this by decreasing the efficiency of the non-freeway roads, or increasing the cost of using the roads, which both only ‘solve’ the problem by reducing general quality of life (especially for poorer people, who might just get even poorer if they can’t commute affordably). Or you can increase road capacity to keep up with population growth, and invest in alternative transport that people actually want to use. That means no cycle lanes or buses, because people really don’t want to use them (buses are only really efficient for short trips, if you have to change buses to get to work then it ends up taking so long you may as well just be inefficiently sitting in the comfort of your own car).
  - kalleboo 8y ago
    > Or you can increase road capacity to keep up with population growth This doesn't work because in a city you'll eventually you end up with more roads and parking lots than buildings. US cities were built like this, and the more road capacity you build, the more sprawl you get (everything is further apart), which increases how much people have to drive which increases the traffic... It's an evil spiral of congestion.
danmaz74 8y ago
In dense city environments, it's just physically impossible to build enough capacity to meet the potential demand for car rides at peak hours without congestions. You may hate public transportation, but than is the only solution that demonstrably work, together with scooters and yes, even bikes where geography and weather make them viable.
hcurtiss 8y ago
Exactly. I live in a small town. We have no traffic jams, and never have. I believe that proves it’s possible to build sufficient infrastructure to eliminate or reduce traffic jams. It’s just that most large cities elect not to.
- wjnqx 8y ago
  I don't think the cost of that is justified in large cities. LA already dedicates more land area to automobile infrastructure than anything else, and the region is still plagued by traffic jams. At the end of the day, a single rail line can bring an amount of people in and out a city equivalent to multiple lanes of traffic. That's a lesson Americans forgot after 1945 for whatever reason, and now we have to re-learn it from the rest of the world now that we've hit the limits of car-oriented development.
- mantas 8y ago
  Dense large cities are economically unviable if you try to accommodate car traffic. The tale of them being cheaper is true only if you give up large living spaces and personal transport.
- dmoy 8y ago
  Or perhaps for a large enough city, you can't build enough roads, because you'd need like >70% of all area for roads and parking. The scaling doesn't work. For another similar example, think of how much percentsge space you need in a 2 story building devoted to elevators (almost none) vs a 200 story building (a significant percentage of the middle core of the building is nothing but elevators). Take that and scale it even worse, and you have roughly the small town vs big city traffic issue.
- deleted 8y ago
  [deleted]
- quotemstr 8y ago
  Yep. Induced demand is a nuanced concept that's been perverted by a certain community of activists into "science says you can't build enough roads so let's not build any!!!!1111". The truth is that you can, in fact, build enough roads to reduce congestion. It may be too expensive. The road land use fraction may be too high. There may be political problems. All of these factors have to be taken into account before deciding to build more roads. Nevertheless, it is physically possible to build enough roads, and anyone who doesn't acknowledge this basic reality isn't having a serious conversation.

arkh 8y ago

But: isn't it a good thing? More traffic is what those roads are for. More traffic means more activity. Focusing only on the capacity / congestion couple is myopic. If you really want 0 traffic just remove all roads: not sure the side effects will be as easily dismissed.

closeparen 8y ago

The goal of transportation infrastructure is to move people to their destinations quickly. It turns out that adding road capacity moves more people, rather than moving the same people more quickly, but that's still a success case. If we should reject road expansion because it fails to decrease travel times, then we should certainly reject a shift towards public transit, which actively makes them much worse. "Congestion" is a non-problem. You get no points for "solving congestion" by kicking everyone off the road. It's quite likely that a highly congested road is still delivering better end-to-end travel times and user experience than a realistic bus system. "Solving congestion" is great for you if you can afford the congestion charge, but it's not clear why a democratic society should let the rich kick the poor off the roads for their personal convenience. Really the only angle under which it's a coherent goal is reducing carbon emissions, but then you don't even need to talk about induced demand - it's sort of obvious that more road capacity means more driving.

pasabagi 8y ago
Why does public transit increase travel times? Good public transport is far more efficient than car-driving, for the simple fact that you can fit fifty people on a bus, and five hundred on a train. This massively alleviates congestion, is vastly more mechanically efficient, and massively simplifies planning. In a city with bicycle lanes, bikes are a lot faster than cars for short trips, and they require far less infrastructure - since bike lanes are about a third of the width of a road, and they require no dedicated parking space. Not to mention the fact that bikes are far cheaper to own and operate. I can understand having a sentimental attachment to cars - but in practical terms, they're a ridiculous solution to the problem of mass transit.
- closeparen 8y ago
  >Why does public transit increase travel times? Because we don't all share an origin, destination, and schedule. Public transit can be extremely effective for the parts of the journey that it covers, but the extreme ineffectiveness of walking the other parts can cancel all that out. You have to completely rethink density and development patterns to get to a point where most origins and destinations are near stations. That would take decades even if we wanted to do it, and SB827 was just defeated in California. Then you have to run trains frequently enough that schedules don't matter. That's expensive as hell and the necessary capital projects take decades. And even if you do them, they might deteriorate and regress later if you don't keep up with the maintenance (see: New York). When I lived in Berkeley, BART covered 90% of my commute distance, station to station, in 25 minutes. My actual end-to-end commute time was over an hour, basically a wash compared to taking an Uber over the Bay Bridge at rush hour. Bicycling to my local station got it down to maybe 50. 25 minutes is an entire commute the average American. Being just 1.5 miles away from a station doubled that. Public transit has a wickedly hard problem to solve - even 90% coverage is still next to useless.