4 ms·

The issue is not that induced demand exists (it exists for nearly every kind of travel) but that the cost-benefit ratio for highways is actually rather low, bec

The issue is not that induced demand exists (it exists for nearly every kind of travel) but that the cost-benefit ratio for highways is actually rather low, because highway lanes are so low capacity and fill up fast. (A standard metro line can easily carry 30-60k persons per direction per hour; the figure for a highway lane is 2.5k.) US highway transportation funding is not generally subject to cost effectiveness analysis but distributed according to formulas to the 50 states and funded at a 90-10 federal-local ratio, which is very different from how other modes of transportation are funded. Quite frankly, it is impossible to build your way out of highway congestion, without totally gutting American metropolitan areas, because there isn't just empty land in the middle of those for new highways. Which is also the root cause of most highway opposition these days, in existing areas; but new areas are not much better, in that usually this results in playing musical chairs with regional development rather than totally new net growth.

rayiner 4y ago
> but that the cost-benefit ratio for highways is actually rather low, because highway lanes are so low capacity and fill up fast. (A standard metro line can easily carry 30-60k persons per direction per hour; the figure for a highway lane is 2.5k.) That’s not the complete cost benefit calculation. A 4-lane highway costs $5-10 million per mile in suburban areas. Meanwhile, the DC Metro’s recent expansion through exurban Virginia mostly along an existing right of way cost $200 million per mile: https://www.heritage.org/transportation/commentary/washingtons-new-6-billion-metro-line-needs-simpler-solutions https://www.heritage.org/transportation/commentary/washingto.... So even if the rail carries three times as many people, it costs 20 to 40 times as much money per mile. That’s the cost side. On the benefit side, few places can saturate a subway line that carries 30,000 passengers per hour. Over the Thanksgiving weekend, just 5,000 people per day used the new Silver Line stops in Virginia. Even the design estimate of the Silver Line was 30,000 per day, and actual use has been a fraction of that. So the benefit side of the equation is a lot lower than the theoretical peak.
- bobthepanda 4y ago
  It makes more sense to compare like for like. The current project to expand I-66 in the DC suburbs of Virginia is $3.7B, which is $160M per mile along an existing right of way.
  - rblatz 4y ago
    How many lanes are being added as part of this expansion?
    - bobthepanda 4y ago
      Two lanes in each direction. https://www.fhwa.dot.gov/ipd/project_profiles/va_transform_66.aspx https://www.fhwa.dot.gov/ipd/project_profiles/va_transform_6...
      - danny_codes 4y ago
        So about 10x more expensive per person hmm
  - rayiner 4y ago
    Only $2.3 billion is for construction of the express lanes, so $100 million per mile. And it’s not like with like. The Silver line was constructed on an existing median that had been reserved for it decades ago. The I-66 express lane expansion required buying more land alongside the existing right of way. The 4 new express lanes will also carry 5,000 vehicles per hour in each direction, which is as much as the total ridership of the Silver Line (outside the Beltway) in an entire day. Also, the actual cost to the state will be much lower. People highly value point to point driving access. So the express lanes can charge tolls up to $40.
- bobthepanda 4y ago
  > On the benefit side, few places can saturate a subway line that carries 30,000 passengers per hour. It should be noted, that this is actually pretty good; this is an investment that will last decades, because it will take that long to fill it up, whereas a highway investment will easily need to be repeated over, and over, and over again. (There's a joke that in some states there are two seasons: winter and road construction.)

rayiner 4y ago

> but that the cost-benefit ratio for highways is actually rather low, because highway lanes are so low capacity and fill up fast. (A standard metro line can easily carry 30-60k persons per direction per hour; the figure for a highway lane is 2.5k.) That’s not the complete cost benefit calculation. A 4-lane highway costs $5-10 million per mile in suburban areas. Meanwhile, the DC Metro’s recent expansion through exurban Virginia mostly along an existing right of way cost $200 million per mile: https://www.heritage.org/transportation/commentary/washingtons-new-6-billion-metro-line-needs-simpler-solutions https://www.heritage.org/transportation/commentary/washingto.... So even if the rail carries three times as many people, it costs 20 to 40 times as much money per mile. That’s the cost side. On the benefit side, few places can saturate a subway line that carries 30,000 passengers per hour. Over the Thanksgiving weekend, just 5,000 people per day used the new Silver Line stops in Virginia. Even the design estimate of the Silver Line was 30,000 per day, and actual use has been a fraction of that. So the benefit side of the equation is a lot lower than the theoretical peak.

bobthepanda 4y ago
It makes more sense to compare like for like. The current project to expand I-66 in the DC suburbs of Virginia is $3.7B, which is $160M per mile along an existing right of way.
- rblatz 4y ago
  How many lanes are being added as part of this expansion?
  - bobthepanda 4y ago
    Two lanes in each direction. https://www.fhwa.dot.gov/ipd/project_profiles/va_transform_66.aspx https://www.fhwa.dot.gov/ipd/project_profiles/va_transform_6...
    - danny_codes 4y ago
      So about 10x more expensive per person hmm
- rayiner 4y ago
  Only $2.3 billion is for construction of the express lanes, so $100 million per mile. And it’s not like with like. The Silver line was constructed on an existing median that had been reserved for it decades ago. The I-66 express lane expansion required buying more land alongside the existing right of way. The 4 new express lanes will also carry 5,000 vehicles per hour in each direction, which is as much as the total ridership of the Silver Line (outside the Beltway) in an entire day. Also, the actual cost to the state will be much lower. People highly value point to point driving access. So the express lanes can charge tolls up to $40.
bobthepanda 4y ago
> On the benefit side, few places can saturate a subway line that carries 30,000 passengers per hour. It should be noted, that this is actually pretty good; this is an investment that will last decades, because it will take that long to fill it up, whereas a highway investment will easily need to be repeated over, and over, and over again. (There's a joke that in some states there are two seasons: winter and road construction.)