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Adding 10 percent more road capacity leads to 3-6 percent more vehicle miles in the near term and 6-10 percent more over many years. So... sounds like less tra

Adding 10 percent more road capacity leads to 3-6 percent more vehicle miles in the near term and 6-10 percent more over many years. So... sounds like less traffic. Wonder why the title says "more traffic". Some of the cars on a new highway lane have simply relocated from a slower alternative route. But many are entirely new. They reflect leisure trips that often go unmade in bad traffic, or drivers who once used transit or carpooled, or shifting development patterns, and so on. Those all sound like good things. The point of roads is to use them. So people use them to have a shorter commute, or live a bit further away from work to lower rent, etc etc etc. What is the actual problem? Did anyone actually expect that building more roads would lead to no increase in road usage?

codeulike 11y ago
Because there are alternatives that also increase people's mobility, as 'hammock' wrote below: "the alternative to falling into the induced demand trap by building more roads, is to improve public transportation infrastructure. Such improvement has been shown, perhaps counterintuitively, to have the biggest effect on road traffic."
thehenster 11y ago
"Did anyone actually expect that building more roads would lead to no increase in road usage?" I think that's exactly it. Perhaps all road building initiatives should be publicised as short term congestion relief and long term preference of cars over other forms of transport.
lhopki01 11y ago
The problem is you get into an endless cycle of adding more and more road capacity and still ending up with the same amount of congestion. If you invest that money in public transport or cycle infrastructure you end up lowering congestion and speeding up everyone's movement including those that still want to drive.
- dumbmatter 11y ago
  I still don't see why "Adding 10 percent more road capacity leads to 3-6 percent more vehicle miles in the near term and 6-10 percent more over many years" is being interpreted as "ending up with the same amount of congestion". If public transit or bike lanes would provide a better benefit for the same cost, then I would support them. But that's a separate and complicated discussion. Instead, this article seems designed to mislead people into thinking that expanding roads has literally no benefit, when obviously it does even if congestion remained the same (which it doesn't). Maybe I'm too cynical...
  - lhopki01 11y ago
    Well first congestion isn't linear to vehicle miles. In traffic movement small things have a massive knock on effect. On my daily route to work I see the effect that adding just a few more cars to a road does. Adding 5% more cars doesn't increase congestion by 5% it actually brings traffic to a standstill where it was moving at an effective pace before. Adding extra capacity can even make the problem worse because of what happens when increased capacity meets lower capacity. Human driver are terrible at going from two lanes down to two. You could say that this is bad design but in cities especially there are constraints that you can't really design around very easily without destroying massive parts of the city. This was done in the past to allow highways to penetrate right into cities but those highways just slowed to a crawl. As for cost effectiveness bike lanes are a lot cheaper than extra road lanes and very much cheaper than elevated highways. Bus rapid transit is also extremely cheap. That's before you start looking at other cost benefits such as increased health for more exercise and less pollution.
    - Dylan16807 11y ago
      >Adding 5% more cars doesn't increase congestion by 5% it actually brings traffic to a standstill where it was moving at an effective pace before. That seems to argue in favor of the expansion. The 10% road increase may only lead to a 4% decrease in car density, but that could be enough to bring traffic out of standstill.

codeulike 11y ago

Because there are alternatives that also increase people's mobility, as 'hammock' wrote below: "the alternative to falling into the induced demand trap by building more roads, is to improve public transportation infrastructure. Such improvement has been shown, perhaps counterintuitively, to have the biggest effect on road traffic."

thehenster 11y ago

"Did anyone actually expect that building more roads would lead to no increase in road usage?" I think that's exactly it. Perhaps all road building initiatives should be publicised as short term congestion relief and long term preference of cars over other forms of transport.

lhopki01 11y ago

The problem is you get into an endless cycle of adding more and more road capacity and still ending up with the same amount of congestion. If you invest that money in public transport or cycle infrastructure you end up lowering congestion and speeding up everyone's movement including those that still want to drive.

dumbmatter 11y ago
I still don't see why "Adding 10 percent more road capacity leads to 3-6 percent more vehicle miles in the near term and 6-10 percent more over many years" is being interpreted as "ending up with the same amount of congestion". If public transit or bike lanes would provide a better benefit for the same cost, then I would support them. But that's a separate and complicated discussion. Instead, this article seems designed to mislead people into thinking that expanding roads has literally no benefit, when obviously it does even if congestion remained the same (which it doesn't). Maybe I'm too cynical...
- lhopki01 11y ago
  Well first congestion isn't linear to vehicle miles. In traffic movement small things have a massive knock on effect. On my daily route to work I see the effect that adding just a few more cars to a road does. Adding 5% more cars doesn't increase congestion by 5% it actually brings traffic to a standstill where it was moving at an effective pace before. Adding extra capacity can even make the problem worse because of what happens when increased capacity meets lower capacity. Human driver are terrible at going from two lanes down to two. You could say that this is bad design but in cities especially there are constraints that you can't really design around very easily without destroying massive parts of the city. This was done in the past to allow highways to penetrate right into cities but those highways just slowed to a crawl. As for cost effectiveness bike lanes are a lot cheaper than extra road lanes and very much cheaper than elevated highways. Bus rapid transit is also extremely cheap. That's before you start looking at other cost benefits such as increased health for more exercise and less pollution.
  - Dylan16807 11y ago
    >Adding 5% more cars doesn't increase congestion by 5% it actually brings traffic to a standstill where it was moving at an effective pace before. That seems to argue in favor of the expansion. The 10% road increase may only lead to a 4% decrease in car density, but that could be enough to bring traffic out of standstill.