5 ms·

Please stop adding more lanes to busy highways – it doesn’t help

22 points by alexrustic 5y ago

handmodel 5y ago
I am a huge proponent of better public transit but I think pointing out induced demand and saying extra lanes has no benefits is misleading. If four lanes can handle 10,000 cars an hour at 45mph and six lanes can handle 15,000 cars an hour at 45mph then induced demand pointer-outers will point out that this doesn't help the traffic. And this is true! But clearly if the goal is for a city to get as much cars through as possible + make as many houses in the range of distance that can commute this is a plus. This creates lots of problems with carbon waste and sprawl but I think looking at the traffic issue alone doesn't capture the full picture. It's like telling a restaurant that has an average wait time of 20 minutes that if they build 50% more tables and improve their wait staff that they will still have 20 minute wait times on Friday. This is true - but the wait time being held constant while drastically increasing capacity accomplishes the stated goals. And I have a hunch a lot of this criticism probably comes from a place of wealthier people who live within a very short distance of their place of work.
- eppp 5y ago
  Is that ever the stated goal or complaint? Anecdotally of course, but I have never heard anyone in traffic wish that the road could carry even more cars at a higher rate. They want there to be less traffic. Building more lanes never accomplishes this. Take Atlanta for instance, something that would actually help traffic would be to build bypasses with no on ramps that circle the city. Every time they build a new loop so that truck traffic can bypass, more houses are built near that loop.
  - zamadatix 5y ago
    It's hard to separate the two in casual conversation if you're not explicitly intending to. E.g. if someone says "it's a bad time to drive into the city I should do it later" it's easy to interpret that as "there is too much traffic there would need to be less" but it's the exact use case adding another lane allows, more cars decide to come in until the pressure is enough that for additional cars "it's a bad time...". Same with the houses, they instantly popup because there is now more capacity to take people in where there wasn't before. Clearly you can't build enough roads to satisfy this relationship to the point the physical distance the car can reasonably travel in a day is the limiter instead of the number of cars that can make it should there be a road available to fit them which is why it's not an answer for congestion in large cities but it can be the answer to capacity into target cities (barring enough support for more efficient means like mass transport).
  - handmodel 5y ago
    I 100% agree that the person in the car is only thinking of themselves and wants traffic time reduced. But I don't think that is the goal of the people building the highways. They are thinking of how to maximize the economic output of a city + connect people to areas they currently have no access to. In your example it is a huge win for the city that new houses can be built in areas that have quick access to the highway and therefore the city. You (the incumbent) may not benefit but the number of people that now have a similarly nice experience to the people that already live close enough to the city to have access will increase.
at-fates-hands 5y ago
They're still using Turner's paper about "induced demand" but when you look at the data, it doesn't really support the hypothesis: https://www.cato.org/blog/debunking-induced-demand-myth https://www.cato.org/blog/debunking-induced-demand-myth The paper compared daily kilometers of interstate highway driving with lane kilometers of interstates in the urbanized portions of 228 metropolitan areas. In the average metropolitan area, it found that between 1983 and 1993 lane miles grew by 32 percent while driving grew by 77 percent. Between 1993 and 2003, lane miles grew by 18 percent, and driving grew by 46 percent. That's hardly a "perfect one-to-one relationship." The paper also calculated the elasticities of driving in relationship to lane kilometers. An elasticity of 2 would mean a 10 percent increase in lane miles would correspond with a 20 percent growth in driving; an elasticity of 1 would mean that lane miles and driving would track closely together. The paper found that elasticities were very close to 1 with standard errors of around 0.05. Even though this is contradicted by the previously cited data showing that driving grew much faster than lane miles, this is the source of Turner's "perfect one-to-one relationship." Looking at the same years as Duranton & Turner, in more than 90 percent of urban areas, driving grew far faster than lane miles. On average, driving grew more than twice as fast as lane miles. But in Boston between 1983 and 1993, freeway capacities grew by less than 1 percent, while driving grew by more than 35 percent. In Madison, capacities grew by 35 percent, while driving grew by less than 20 percent. The wide range in differences between urban areas suggests that, not only are Duranton & Turner's elasticities wrong, their standard errors are far too low.
WheelsAtLarge 5y ago
Our local 405 FWY section was expanded by one lane thanks to the governmental stimulus spending after 2008. It took years and in some sections it ruined the view since they had to chop thru a few hillsides to expand the freeway. It took years and we had to deal with the constant closures and extra traffic. It seemed like a great project and we were hoping the extra lane would reduce traffic. Now, many years later after they finished, to me it's still the same constant congestion. We still need to go thru heavy traffic on the way to work and back. I suspect that if you make a detailed study you would find a difference but as a practical matter, traffic did not change. The billions of dollars the construction cost would have been better used to expand the public transportation system.I think this article has a going point.
GekkePrutser 5y ago
Good public transport does really help. I live in a big city with lots of it and I really love not needing a car anymore. Gone is the worry about damage, accidents, fines for missing a speed sign, whether I topped up the parking meter in time, costly repairs and insurance bills. Not to mention the stress of driving and all the wasted hours. I never thought of it as providing me with freedom, instead it felt like a necessary ball and chain. Now I can go where I please for peanuts with no worries and no constraints (eg always having to go back to where I parked). But public transport needs to be excellent and affordable for this to work.
- asddubs 5y ago
  I live in a place with good public transport and generally prefer it to taking the car, although corona has me a bit antsy about it these days
  - mycall 5y ago
    https://www.bbc.com/news/health-51736185 https://www.bbc.com/news/health-51736185
    - asddubs 5y ago
      not really sure what this is supposed to tell me
atatatat 5y ago
If you move back to the right when you're done passing it sure as fuck does. I get more done in 7 lanes of rush hour traffic in California than anywhere else.

22 points by alexrustic 5y ago

I am a huge proponent of better public transit but I think pointing out induced demand and saying extra lanes has no benefits is misleading. If four lanes can handle 10,000 cars an hour at 45mph and six lanes can handle 15,000 cars an hour at 45mph then induced demand pointer-outers will point out that this doesn't help the traffic. And this is true! But clearly if the goal is for a city to get as much cars through as possible + make as many houses in the range of distance that can commute this is a plus. This creates lots of problems with carbon waste and sprawl but I think looking at the traffic issue alone doesn't capture the full picture. It's like telling a restaurant that has an average wait time of 20 minutes that if they build 50% more tables and improve their wait staff that they will still have 20 minute wait times on Friday. This is true - but the wait time being held constant while drastically increasing capacity accomplishes the stated goals. And I have a hunch a lot of this criticism probably comes from a place of wealthier people who live within a very short distance of their place of work.

eppp 5y ago
Is that ever the stated goal or complaint? Anecdotally of course, but I have never heard anyone in traffic wish that the road could carry even more cars at a higher rate. They want there to be less traffic. Building more lanes never accomplishes this. Take Atlanta for instance, something that would actually help traffic would be to build bypasses with no on ramps that circle the city. Every time they build a new loop so that truck traffic can bypass, more houses are built near that loop.
- zamadatix 5y ago
  It's hard to separate the two in casual conversation if you're not explicitly intending to. E.g. if someone says "it's a bad time to drive into the city I should do it later" it's easy to interpret that as "there is too much traffic there would need to be less" but it's the exact use case adding another lane allows, more cars decide to come in until the pressure is enough that for additional cars "it's a bad time...". Same with the houses, they instantly popup because there is now more capacity to take people in where there wasn't before. Clearly you can't build enough roads to satisfy this relationship to the point the physical distance the car can reasonably travel in a day is the limiter instead of the number of cars that can make it should there be a road available to fit them which is why it's not an answer for congestion in large cities but it can be the answer to capacity into target cities (barring enough support for more efficient means like mass transport).
- handmodel 5y ago
  I 100% agree that the person in the car is only thinking of themselves and wants traffic time reduced. But I don't think that is the goal of the people building the highways. They are thinking of how to maximize the economic output of a city + connect people to areas they currently have no access to. In your example it is a huge win for the city that new houses can be built in areas that have quick access to the highway and therefore the city. You (the incumbent) may not benefit but the number of people that now have a similarly nice experience to the people that already live close enough to the city to have access will increase.

at-fates-hands 5y ago

They're still using Turner's paper about "induced demand" but when you look at the data, it doesn't really support the hypothesis: https://www.cato.org/blog/debunking-induced-demand-myth https://www.cato.org/blog/debunking-induced-demand-myth The paper compared daily kilometers of interstate highway driving with lane kilometers of interstates in the urbanized portions of 228 metropolitan areas. In the average metropolitan area, it found that between 1983 and 1993 lane miles grew by 32 percent while driving grew by 77 percent. Between 1993 and 2003, lane miles grew by 18 percent, and driving grew by 46 percent. That's hardly a "perfect one-to-one relationship." The paper also calculated the elasticities of driving in relationship to lane kilometers. An elasticity of 2 would mean a 10 percent increase in lane miles would correspond with a 20 percent growth in driving; an elasticity of 1 would mean that lane miles and driving would track closely together. The paper found that elasticities were very close to 1 with standard errors of around 0.05. Even though this is contradicted by the previously cited data showing that driving grew much faster than lane miles, this is the source of Turner's "perfect one-to-one relationship." Looking at the same years as Duranton & Turner, in more than 90 percent of urban areas, driving grew far faster than lane miles. On average, driving grew more than twice as fast as lane miles. But in Boston between 1983 and 1993, freeway capacities grew by less than 1 percent, while driving grew by more than 35 percent. In Madison, capacities grew by 35 percent, while driving grew by less than 20 percent. The wide range in differences between urban areas suggests that, not only are Duranton & Turner's elasticities wrong, their standard errors are far too low.

WheelsAtLarge 5y ago

Our local 405 FWY section was expanded by one lane thanks to the governmental stimulus spending after 2008. It took years and in some sections it ruined the view since they had to chop thru a few hillsides to expand the freeway. It took years and we had to deal with the constant closures and extra traffic. It seemed like a great project and we were hoping the extra lane would reduce traffic. Now, many years later after they finished, to me it's still the same constant congestion. We still need to go thru heavy traffic on the way to work and back. I suspect that if you make a detailed study you would find a difference but as a practical matter, traffic did not change. The billions of dollars the construction cost would have been better used to expand the public transportation system.I think this article has a going point.

GekkePrutser 5y ago

Good public transport does really help. I live in a big city with lots of it and I really love not needing a car anymore. Gone is the worry about damage, accidents, fines for missing a speed sign, whether I topped up the parking meter in time, costly repairs and insurance bills. Not to mention the stress of driving and all the wasted hours. I never thought of it as providing me with freedom, instead it felt like a necessary ball and chain. Now I can go where I please for peanuts with no worries and no constraints (eg always having to go back to where I parked). But public transport needs to be excellent and affordable for this to work.

asddubs 5y ago
I live in a place with good public transport and generally prefer it to taking the car, although corona has me a bit antsy about it these days
- mycall 5y ago
  https://www.bbc.com/news/health-51736185 https://www.bbc.com/news/health-51736185
  - asddubs 5y ago
    not really sure what this is supposed to tell me

atatatat 5y ago

If you move back to the right when you're done passing it sure as fuck does. I get more done in 7 lanes of rush hour traffic in California than anywhere else.