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    Re: Unwarranted levels of precision
    From: Gary LaPook
    Date: 2017 Dec 20, 08:20 -0800

    From: David Pike
    Date: 2017 Dec 20, 01:06 -0800

    Even two mph over the limit couldn't make a difference since they have much larger safety margins built in when they set a speed limit.

    I was researching automotive speed control some years ago, and one of the things I noticed was that in accidents involving bends  relatively small increases in speed can make a significant difference in the force required to keep the vehicle on the road, (or I suppose trains on tracks).  This is because the centripetal and centrifugal forces involved increase with the square of the speed.  E.g.  If the recommended speed for a car on a bend is 30mph, taking the bend at 35mph means a 17% increase in speed but a 36% increases in forces required.  With a train, such oversight might cause the carriages to topple outwards off the track or the outside track to give way.  Then as the wreck is brought to a halt the energy to be dissipated (and therefore damage done) also depends upon the square of the speed.  Either way, exceed speed limits with caution.  DaveP 


    My friend, Paul, has posted many educational segments in the form of "puzzles." Amoung the many things he has done is teach engineering at UCLA, he used to live in the Bay Area but he married a French woman and they now live in Brittany. He has a "puzzle" exactly on your  topic of speed control of trains at:


    you might find it of interest.

    I met him while discussing navigation of the Earhart flight and he has some "puzzles" on his site regarding celestial navigation that you also might like:


    This is the kind of work he did in the states too:



    • Technical Consultant to Management

      ExpressLocal in France
       – Present (6 years)

      Independent technical studies for railroad properties and proposals on behalf of train control suppliers, formal design reviews and presentation packages.

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