[PRCo] Re: Cab Signals vs Wayside Signals - Baltimore & Lease Back Financing

[Phillip Clark Campbell]

> ----- Original Message ----


> the signal system was changed when they did the
> double tracking.  From wayside signals with
> inductive train stop to a cab signal system. 
> .... 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."


Mr.Schneider;


Very informative summary from Mr.Anonymous isn't it.  I lived in San Francisco (Parkside) in the early 1980s when the Boeing cars were introduced and they used cab signals in the subway didn't they.  Operators found a way to overcome the bone chilling stops when the computer took over because it perceived the braking rate was insufficient thus dumping it into emergency.  The operators turned the reverser key to neutral which effectively puts the car in park doesn't it.  Thus only the disc brakes are applied to complete the stop which is then much smoother.

Operators stated that they had 3-seconds to react when given a reduced speed by the cab signals which meant putting the controller into full service brake mode.  Once the car slowed to below the posted cab speed the operator could then apply power if needed.  If the computer sensed that the braking was insufficient then the car would be dumped into emergency and the astute operator would put the reverser in neutral.

Some operators anticipated the speed change and slowed the car approaching the impedance bonds which made for a much smoother ride without bone chilling stops.  Other operators rode over the bonds - knowing that they would get a slower speed demand - and then placed the car into full service when that demand was realized.  By the time the computer returned control to the operator the car slowed well below the posted speed and had to be brought back up only to have the same happen at the next impedance bond.

If the operator did not respond fast enough to speed changes then
control would be taken away from the operator altogether and the car
would need to make a complete stop before control was restored wouldn't it.

I do not know if other rail cars could be put into neutral as the Boeings.

I totally overlooked the fact that signaling is used.  This rules out sanding whether wayside or cab signals doesn't it.  Wayside signals replaced because of human error and accidents; cab signals cause other problems.  Every thing has 'side effects' doesn't it.

In another post you mentioned Sacramento being caught up in the AIG fiasco.  BART has to come up with $40-million fast for the same reason - AIG.  Another news item said that SF Bay Area transit systems have 'several hundred' of such lease back loans.  What other systems are involved?  I haven't heard more.  Here are two quotes from the URL below:

"San Francisco made several hundred millions of dollars worth of deals,..."

"Transit agencies, then, are like crack addicts, addicted to the quick
benefits of loans, leases, and other poorly considered deals."

http://thetransportpolitic.wordpress.com/2008/10/26/short-term-thinking/



Phil