On 18 Nov 2011, at 16:48, Clive D.W. Feather wrote: > Paul J. Ste. Marie said: >>> Hmm. In the UK the working timetable (not the public one) is written to a >>> precision of half a minute. >> This wasn't the timetable. Its main purpose, as I understood it, was to >> provide a record of where trains were, or where the dispatchers thought they >> were, in the event of an accident. > > Okay. > >> The logged locations weren't stops on the lines. > > Hmm, they may well be logging each track circuit transition
Track circuits? In manually-signalled USA? Anyway, the average freight train in the USA is 6500 feet long (ie substantially over a mile) and travels at an average of around 20mph, or at most 30mph. So it takes around two minutes to pass a point. Timing that to a precision of a second seems a excessive. Each vehicle is of the order 20m long, so at those sorts of speed is going to take over a second to pass. ian _______________________________________________ LEAPSECS mailing list LEAPSECS@leapsecond.com http://six.pairlist.net/mailman/listinfo/leapsecs
