Since an ADVANCE WARNING SIGN is placed two miles ahead of the location where the lower speed applies, what about the situation where two speed are separated less than two miles (second lower than first)? Is there an advance warning sign, then an lower advance warning sign, then the first speed sign, then the lower speed sign? Or the second advance warning sign omitted or placed less than two miles, after the first speed sign to avoid confusion?
Not uncommon to have ‘nested’ or overlapping ‘slow orders’ like that, much to the frustration of the train crews who have to traverse them once or twice a day, for days on end.
But they could have been placed by different ‘crafts’ or departments (C&S vs. MOW), different crews or reasons even within the same craft (different track problems), and for different time frames, etc. So it’s a lot simpler, more reliable, and hence safer for each crew to be responsible for implementing and removing their own speed restrictions only, rather than having to coordinate and match schedules with those crews responsible for the other slow orders, which would be necessary to be able to simplify them as you suggest. And “Murphy’s Law” tells us that sooner or later, it’s guaranteed that someone will screw up that coordination.
That being said, if the situation looks like it’s going to persist for a long time - like all winter, or until the next Tie & Surfacing gang comes through - common sense would suggest rationalizing the situation with a broader order, if someone in the Transportation Dept. hierarchy can be persuaded that it’s worth their while to do so.
Such situations are generally resolved by one of two occurences.
1, Train crew blows one of the slow orders and the overlappng nature is brought up in the subsequent disciplinary investigation.
Chief Operating Officer is making a inspection trip over the territory - Division officials will clean up all the train messages - slow orders - and anything else they can before the trip.
Usually boards (flags/signs etc) are placed for each restriction. If they aren’t displayed or are displayed short, that fact has to be in writing. Distance between the slows doesn’t matter. Say you have a 40mph slow from MP202 to MP203, boards will be normally displayed at MP200 and MP205 for approaching trains. Say a foreman places a 30mph between MP203 and MP204, the boards for that one will be displayed at MP201 and MP206 for approaching trains. So trains in one direction will see a yellow board at MP200 and another one at MP201, the one in the opposite directions at MP205 and MP206.
Slow orders can also overlap and the boards are placed accordingly. Except on certain authorized subdivisions, crews will have all slows, etc in writing. They either get them when they go on duty off a printer/fax or via radio from the dispatcher when one has been added after they’ve left the terminal.
If a crew comes across an unannounced yellow board (except on those mentioned subdivisions), one that doesn’t appear in their paperwork, it’s to be treated as a 10mph restriction until the rear of train is 4 miles from the yellow sign and the dispatcher has confirmed there is no restriction in effect at that location.