[PRCo] The Baltimore debacle

[Schneider Fred]

This came from the "cynical engineer in New Jersey" regarding the
Baltimore screw up that caused them to cripple so many cars that
the entire north end of the Central Light Rail Line had to be removed
from service.  Let's be kind and let the Curmudgeonous Maximous
remain nameless.   It should be sufficient to say he knows the
business.   He's been in it for half a century.   The quotes surround
his words.

"As suspected, it is not that the trees only now started dropping leaves
after a dozen or so years of operation, but that the signal system was
changed when they did the double tracking.  From wayside signals with
inductive train stop to a cab signal system.  Unless a cab signal system
is installed with a lot of care and attention to the operating
environment, this is the kind of mess you are likely to wind up with.
The basic reason is that the principal downside to cab signals from an
operations standpoint is that the operator has no way to act
preemptively.  With wayside signals the operator has the ability to know
that a speed reduction is in the offing and it allows him to apply
brakes conservatively when he knows rail adhesion is poor.  Cab signals
do not allow that; the signal aspect drops instantly without prior
warning, and he has to apply braking immediately at a braking rate that
has been chosen, most likely, by someone with no idea of the operating
environment.

"Left to their own devices, signal engineers will always require that  
the
train be placed in full service braking when it is given a more
restrictive signal aspect, and if the rail adhesion is poor and the
train cannot achieve the requested braking rate, their "Brake Assurance"
feature will eventually dump the train in emergency.  And then, since
signal engineers do not consider the slide control designs on the
railcar to be equivalent to their "Fail Safe" cab signal design, they
will insist that after so many seconds of attempting to correct sliding
wheels it is required that the slide protection be turned off (assuming
that the rail car originally had slide protection in emergency) and thus
force the train to slide to a stop with locked wheels.  For the signal
engineer, flat wheels warm the heart, as they prove that their system
worked.

"If you are a neophyte and unaware of all the nuances and potential
landmines inherent in installing a cab signal system, the below is what
you are likely to wind up with."