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How Electric Cars Could Make America's Crumbling Roads Even Worse

posted by Fnord666 on Tuesday February 26 2019, @02:36PM   
from the exceedingly-crumbly dept.

Phoenix666 writes:

Phys.org:

To fix the potholes and crumbling roads, federal, state and local governments rely on fuel taxes, which raise more than US$80 billion a year and pay for around three-quarters of what the U.S. spends on building new roads and maintaining them.

I recently purchased an electric car, the Tesla Model 3. While swerving down a particularly rutted highway in New York, the economist in me began to wonder, what will happen to the roads as fewer and fewer cars run on gasoline? Who will pay to fix the streets?

Will toll roads become universal to bridge the funding gap?

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Original Submission

• Re:Pretty simple solution to that. Re:Pretty simple solution to that. (Score: 0) by Anonymous Coward on Wednesday February 27 2019, @12:23AM (2 children)

  by Anonymous Coward on Wednesday February 27 2019, @12:23AM (#807368)

  The amount of energy a car uses to move is a good proxy for road wear.

  Bullshit.
  The only deficiency of mileage is that it doesn't include vehicle weight, which is by far the biggest factor in road wear. And at least for cars and light trucks, this is trivially accounted for by considering the vehicle's weight from the registration database. (For commercial trucks, on the other hand, the actual vehicle weight may vary a factor of two or more depending on loading.)
  Power usage isn't an improvement, as it has a lot more to do with acceleration habits and traffic anticipation than with vehicle weight, and these have no significant relation to road wear.

  Parent

• Re:Pretty simple solution to that. Re:Pretty simple solution to that. (Score: 0) by Anonymous Coward on Wednesday February 27 2019, @08:07AM (1 child)

  by Anonymous Coward on Wednesday February 27 2019, @08:07AM (#807510)

  Because energy is never about mass X velocity. so that would have nothing to do with . . . are you always this stupid, or only when you post on the intertubes?

  Parent

  • Re:Pretty simple solution to that. (Score: 0) by Anonymous Coward on Thursday February 28 2019, @12:16AM

    by Anonymous Coward on Thursday February 28 2019, @12:16AM (#807891)

    First, you need mass raised to the 4th power or so to reflect actual road wear, so "mass X velocity" won't cut it.
    If we want to get pedantic, road wear is related to axle weight⁴, not mass, but since the current crop of EVs generally have 2 axles and more-or-less symmetric weight distributions, that's practically a constant factor; it's only worth worrying about the distinction when freight trucks start going electric in any kind of scale.

    Because energy is never about mass X velocity

    Pretty much:

    • Air resistance as a force is drag coefficient × frontal area × velocity², so the power is proportional to a·v³, and the energy to travel a given distance at that speed is just a·v². Frontal area is only weakly related to mass, drag coefficient has no relationship (but varies widely between vehicle types in the same weight class), and you've got velocity to the wrong power.
    • Kinetic energy is mass × velocity², and is input each time you accelerate from zero to a given velocity -- it's completely independent of distance traveled once you get up to speed, and thus has fuck-all to do with road wear
    • Rolling resistance modeled as a constant force means power is some coefficient of weight × velocity, which might be what you're thinking of, but energy for a given distance has no velocity dependence. (Actual rolling resistance with car tires is weakly dependent on velocity, but the power is much less than 1.) And of course this is dwarfed by air resistance in highway driving, and by kinetic energy for repeated accelerations in city driving. I guess it's relevant if you're tooling down a back road at 30 miles per hour.
    • Fluid friction (e.g. from journal bearings) actually is force × velocity; this matters for trains, but in road vehicles bearing friction is completely overwhelmed by the rolling resistance of soft tires.

    So yeah, at least in the context of EV energy consumption, energy is never about "mass X velocity".

    are you always this stupid

    no u

    Parent