Railroad Forums 

  • Controlling Trains - Network Rail video

  • Discussion about railroad topics everywhere outside of Canada and the United States.
Discussion about railroad topics everywhere outside of Canada and the United States.

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 #1422717  by philipmartin
 
Controlling trains is what I did from 1957 to 1993. That Uttoxeter box has a lot of white levers, indicating that they are out of service; lever not connected to anything. That's the way it was where I worked and I believe it's the same in the UK. If I understood correctly they don't have wayside signals on the high speed lines, only cab signals. If that's right, how do they handle it when the cab signals on the train fails? They thought of eliminating wayside signals on the Pennsy, where I worked, but didn't do it; kept both kind of signals.
The video says that they only have four signal aspects. The Pennsy needed more than that. From "Signal Aspects from the Rule Books - Railroad Signals of the US." Note that the chart shows cab signals, small. It doesn't show all Pennsy signals, semaphores or color light signals used in Penn Station, New York, for instance.
 #1422752  by JayBee
 
The UK uses just four signal indications except for certain trains at certain locations on the East Coast Main Line (ECML). Everywhere else from most restrictive to least, they are Red, single Yellow, double Yellow, and Green. On the ECML they add another even less restrictive signal indication Flashing Green which allows 140 mph running where track conditions allow for Class 91 electric locomotives pulling rakes of Mark4 coaching stock. What they also have are "Feathers" indicating diverging routes, and "Route Indicators" displaying letter codes for complex routing possibilities.

See the Wkipedia article here https://en.wikipedia.org/wiki/UK_railway_signalling" onclick="window.open(this.href);return false;
 #1423041  by johnthefireman
 
philipmartin wrote:If I understood correctly they don't have wayside signals on the high speed lines, only cab signals. If that's right, how do they handle it when the cab signals on the train fails?
I don't know the answer to that, but I suppose they have a set of rules to govern that contingency just as we do to govern the contingency when the lineside signals fail. But it's a lot easier to take a single train out of service because its in-cab signalling has failed than to operate trains past a failed lineside signal, where the knock-on effect of delays caused by issuing authorisations to pass signals at danger can be immense.
 #1423044  by johnthefireman
 
JayBee wrote:The UK uses just four signal indications except for certain trains at certain locations on the East Coast Main Line (ECML)
If I recall correctly the flashing yellow signals are to do with turning out over points where the speed is lower than line speed. I think previously they used to use the normal four-aspect signals where, even though the route ahead was clear, they would keep the signal in advance of the points at yellow (or in extreme cases red) until the train had almost reached the signal, and then change it to green or yellow respectively. That had the effect of slowing the train down before it reached the points, but then giving it clearance to speed up again witohut actually stopping. However it was rather messy and if the signaller was not on the ball it could result in slowing the train down more than was necessary, or even stopping it, thus losing time. The flashing yellow is a neater solution.
 #1423125  by ExCon90
 
I've read of instances in which the driver expected the signal to clear up as usual on his approach, until one occasion when the home signal was at danger because of a conflicting movement and remained at danger, and when the driver realized it wasn't going to clear up it was already too late to stop in time. I believe the flashing double yellow and yellow were added after a few of those and are intended to eliminate the problem by providing positive assurance that the signal is going to clear up. The New York subway has a similar system (although at much slower speeds), but a lunar white is displayed below the yellow to indicate that the home signal will clear up provided the train doesn't get there too soon.