Signals - Approach Diverging for slow route

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Signals - Approach Diverging for slow route

Postby MattW » Wed Jan 31, 2018 5:20 pm

I understand that some weak route signaled railroads, like Norfolk Southern, will use Red over Red over Green for slower speed routes mixed with higher speed routes, it's still called diverging clear though. How is the distant signal handled? I understand that it's only ever Yellow over Green, never Yellow over Red over Green as would be the case for a speed signaling scheme. How does the engineer know which route they'll take? Do they prepare for the slowest possible route, then upgrade when they see the faster route?
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Re: Signals - Approach Diverging for slow route

Postby Engineer Spike » Fri Jul 20, 2018 3:59 pm

That sounds like an awful delay. Sometimes there aren’t enough indications to adequately address all situations. Burlington used Approach, but then a Restricting signal at slow crossovers.

When we were talking about speed signals, I gave a few examples of an Approach Slow, followed by a Medium Approach, or Medium Approach Medium at the controlled signal. The reason is on account of the short block. They want the train to head for slow speed, but be able to still pick up to medium speed, if the conditions allow. Your example might be done like this for the same reason. Elsewhere we have a single main, and there are two sidings on either side. One had been 25 mph, but was allowed to degrade to 10 mph. The other was newly laid as for a short term project. It had good CWR, and all new ties. It is 25 mph. The old 10 mph siding still is signaled for medium speed. Maybe someday it too will be upgraded. The new siding is signaled for medium speed too. For a solution to know what track is to be taken, they put flashing arrows facing left or right. They are on both the distant signal, and also the controlled signal.
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Re: Signals - Approach Diverging for slow route

Postby Backshophoss » Fri Jul 20, 2018 5:19 pm

In what was CR territory there was an approach aspect called "approach limited" where the bottom/middle unit was flashing green,
The home signal would show "limited clear" or "restricting" to the 10 mph track.
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