Where the UP is/has added CTC in Iowa to the exCNW east/west mainline they have installed wayside signals.
Before where it was ATC/cab signals, the CNW only had wayside signals at interlockings. Even when the CNW put in some small CTC areas, they only placed waysides at the controlled crossover (absolutes) and one advance wayside to prepare you at the crossover to either proceed on the same track past the control point (1to1etc), be prepared to stop at the control point, or be prepared to crossover at the control point(1to2etc).
Why would they add wayside signals? Because if the cab signal fails and you have no wayside signals, we may only run at restricted speed unless you can get an absolute block. With wayside signals, without an absolute block we can run 40mph.
Jeff
[(-D][(-D][(-D][(-D][(-D][(-D][(-D][(-D] How long before the politically correct natzies change the name from “dwarf signal” to “height challenged signal”
It depends on the cab signal and safety features in use.
If all you are equipped with is cab signals with no other train control system, it will stop the train if the engineer takes no action when the cab signal changes to a more restrictive indication, ie clear to advance approach, advance approach to approach etc.
The engr has 6 seconds to acknowledge the change to avoid the penalty brake application.
Once the change has been acknowledged, if the engr does not take action to slow the train to conform with the new indication what happens? Again, without any other train control system, nothing.
Say your on a 70mph intermodal. You’ve been running on a clear cab and clear wayside signals. You are between waysides and all of a sudden the cab changes from clear to restricting. Once the change has been acknowledged, you could keep going at 70 until the cab signal clears up, you run over a rail that just broke, or thru a switch someone opened at the wrong time, or into a box car that just rolled out onto the main line. Of course the rules require you to bring the train down to restricted speed, but with cab signals alone, there is nothing to enforce the requirement.
Jeff
run a red block and the man will give you 30 days to think about,or test drive your job insurance. I know back in th’ day when they full crews. Crews would run red blocks so they could get 30 days off during deer season! Strange but true!
The reason for the dwarf signal is that it governs a non-signaled track. Cab signals would be a nightmare to wire and understand if it also displayed the indication of every siding or spur track as you went by on the main. The cab signals only display the next indication for the track the locomotive is currently occupying.
In nomal operations, the train approaching the main was expected to stop. They had to anyway. (to unlock and throw the turnout) A full-sized mast and signal head would make it harder for the conductor/brakeman to see the indication while standing on the ground waiting to throw the switch.
I know that in some areas dwarfs are used because of restricted clearances. The UP has some around Omaha/Council Bluffs on the main line.
I would say on the sidings, they are used to prevent confusion with a main line signal.
I’m guessing this is not CTC territory. If it was a controlled switch, there would be fixed absolutes protecting the main lines also. The dwarf on the siding is the leaving signal.
I’m used to GCOR, but I’m sure other rule books will have a similiar provision. At hand operated switches in ABS, when the train is ready to leave and the switch is opened, trains must wait 5 minutes to allow block signal protection to be established. Under certain conditions the 5 minute wait is not required. One is if there is a leaving signal that indicates proceed.
The fixed wayside signal indicates the condition of the block you are about to enter. A cab signal indicates the condition of the block you are in. While on the unsignalled siding, the cab signal would be at restricting since the track is not energized. Once the engine reaches a point where an energized signal can be picked up, the cab signal should change to reflect the the condition of the block just entered.
Jeff