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A Major Oversight in the Boring Equation

Discussion in 'Tesla, Inc.' started by henderrj, Jun 9, 2017.

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  1. henderrj

    henderrj Member

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    Capacity does not equal speed times size. On any 12 foot New York sidewalk at least a dozen people pass every second. That's a capacity of 43,200 per hour. Even at an S or sled every 4 seconds, assuming 4 persons per vehicle, the project capacity of a Boring tunnel is only 1 person per second. Speed, now that is good - a walking speed of probably 3 miles per hour would be greatly eclipsed by 120 miles per hour, so each individual person would arrive much, much quicker in the tunnel.

    But what if we could speed that New York Sidewalk to, say, 35 miles per hour? Even if the capacity was only half that of a cement sidewalk we could still deliver a lot of people at a reasonable rate even up to forty miles or so (many commutes of that distance take even longer what with traffic). I'm talking the moving sidewalk idea in a Boring tunnel, of course.


    I've actually thought on the sidewalk idea for some three decades. Even had some write ups, although they escape me right now. Worked with a county council member to see about getting it funded. But the major problem is land - right of way. Above ground it becomes more than difficult. I still think it is a vastly better idea than, say, light rail (a particularly sore subject for King County residents!) but with the tunnels – it becomes almost magic.

    With a capacity of 40,000 per hour you could deliver half the working people of any city with no waiting for the bus or train, no parking issues, and many other benefits. That first is a major benefit – whenever you walk to the station you get on and go – you never, ever wait. Weather, scary people, strange hours, nothing of that sort to bother you. Sit on the benches or walk, even jog, but never, ever wait.

    I’ve worked out most of the problems with moving the “platforms”. How to connect them, how to pull and replace defective (or non responding) units, how to work the expansion joints, even how to stop them quickly in the event of terrorism or a, less likely, catastrophic natural disaster. Entrance and egress, well, that’s a lot more fun! Still, it would be fantastic to see something like this funded. For less than Elon has into his hole drilling company we could have a working prototype. Maybe even put it between the Fremont factory and some cheaper parking areas. Flex scheduling would be no problem, etc.

    So, what thoughts have you all? Or do you even care?!

    (Didn’t know where else to put it so hope this forum is okay.)
     
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  2. Fiddler

    Fiddler Member

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    #2 Fiddler, Jun 9, 2017
    Last edited: Jun 9, 2017
    I took a transportation/traffic queuing theory class at APL, MD some 40 years ago (pre GPS) and one interesting take home:
    "The number of cars crossing a bridge (or stretch of highway) per hour is independent of speed."

    If all the cars are speeding at 100mph or only 10mph the number of cars over the bridge in one hour is the same in steady state. Since the spacing between the cars is proportional to speed, The cars traveling 100mph have ten times the distance between them compared to the 10mph cars. An individual car crosses the bridge sooner with higher speed, but then the number of cars on the bridge is lower.

    Another tidbit was one rail line has the capacity of more than 17 lanes of highway.

    for those interested:
    Modelling Intelligent Multi-Modal Transit Systems
     
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  3. animorph

    animorph Member

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    A moving sidewalk with a people density equal to that hypothetical NY sidewalk moving at 35 MPH would be a disaster of its own if anything gummed up the works and caused it to abruptly stop. Kind of need seats, seat belts, windshields. Plus a lot of persuasion to get people to use it.
     
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  4. Snowstorm

    Snowstorm Member

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    That does not seem intuitively true to me. I can see that at certain range of speeds, but as density increases it looks like you'll reach a point where speed is so slow that increase density doesn't compensate for decrease in speed. Imagine when highway is so packed that it is stop and go.

    I seem to recall that there was some study that showed maximum throughput offered at around 40-50mph. Here is one reference that alludes to something similar https://www.wsdot.wa.gov/NR/rdonlyres/5FF329ED-A840-4F8A-A798-468948BEE80B/0/Maximizing_Highway_Capacity_PM_finalvsn.pdf
     
  5. pilotSteve

    pilotSteve Member

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    "The Roads Must Roll" ... Robert A Heinlein, sci fit author details this idea for people movers in dense cities. From his books n the 1970s!
     
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  6. henderrj

    henderrj Member

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    Yes, had to consider that possibility. Of course any "cars" close to the damage would likely result in injuries, if occupied. But the intelligent coordinated use of expansion joints would allow those further away to slow gradually enough that injuries could be avoided. Of course it could never happen, or so very rarely as to be safer than car travel. sort of like air travel is now - and yet in was supremely dangerous in the early days. We'd just skip the early days with sufficient digital modeling.

    And, keeping with the airline analogy, it is perfectly safe to walk down the aisle of a 767 going 600 miles an hour - as long as it doesn't abruptly change speed or direction. Same thing here. I think resistance would be very low. You'll have more people worried about being underground - but then subways are pretty jammed!
     
  7. henderrj

    henderrj Member

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    Yes, lot's of interesting reading. I believe Asimov beat him by quite a few years. As I recall the first mention of moving sidewalks was in the 1800s!
     
  8. henderrj

    henderrj Member

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    Wonderful input! I'll definitely give that a look.
     
  9. henderrj

    henderrj Member

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    Clearly there would only be a limited speed range where this would work but it does make sense within that range. Really the same thing i was saying - slower speed but, in this case, the same capacity. Need both for the individual traveler but the bridge cares not!
     

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