"TheOneKEA" wrote in message
ps.com...

"Bobbing" is when the signal rapidly changes
from aspect to aspect without warning or reason.

Naturally this is a major problem because a signal
could bob despite an occupied track in front of the
train; thus, if it goes to green and the driver passes
it in the correct way at speed, CRUNCH.

I doubt that, because it would violate the concept of "failsafe".

--
John Rowland - Spamtrapped
Transport Plans for the London Area, updated 2001
http://www.geocities.com/Athens/Acro...69/tpftla.html
A man's vehicle is a symbol of his manhood.
That's why my vehicle's the Piccadilly Line -
It's the size of a county and it comes every two and a half minutes