[LEAPSECS] Schedule for success

[Poul-Henning Kamp]

In message <407EB3F6-55BB-4E60-8D20-C909EA92E6B9 at noao.edu>, Rob Seaman writes:


>Consider the iconic issue of timekeeping for trains, one of the  

>primary drivers for our current standard time zone system.  Trains  

>clearly need to be synchronized with external clocks.  Trains clearly  

>have some mechanism or set of procedures (imperfect or not) for doing  

>so.  So they don't match the question asked.


Modern trains run at speeds of roughly 100 m/s.  They care very much
about seconds and fractions thereof.

In fact, they run so fast that a special version of the GSM mobile
standard called "GSM-R", has been created for train-control
applications.

The main difference between plain GSM and GSM-R is that the latter
allows for dopplershift up to 140 m/s, but now railway people have
started bitching about that not being enough margin.

If you want to know what non-antique rail-road control looks like,
search for and study "ERTMS".

Poul-Henning

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