I can imagine flashing green is some sort of advanced approach or something. Can anybody give me clarity as to what it is?
Seen on the CN Waukesha Sub…Mundelein
Diverging Advance Approach. You’ll be making a turn at the second light. CN at Waukesha has this aspect as well.
Another way to display this is a flashing yellow over green.
I’m certainly no expert, but I believe in Amtrak and SEPTA territory the flashing green - on top ! - is essentially a “super-clear” or “Track Speed” indication.
It matters where the flashing green is, on signals with multiple heads. See the following websites for examples:
http://broadway.pennsyrr.com/Rail/Signal/aspect_concord.html - “Cab Speed” under NORAC rules (at the bottom of this page)
http://www.blet375.com/csx-Signals-REDI-Center.pdf (382 KB file size). From page 18 of 55: “A COLOR FLASHING UPGRADES SIGNAL”.
- Paul North.
[(-D] Well said ! Much clearer than usual. [tup]
- Paul North.
Depends on your railroad. On NYCT’s (L) line it means that CBTC (Computer Based Train Control) is in effect and operating. Sit back and enjoy the ride!
ROAR
I don’t have the current CN (US version) rule or signal charts, but usually when Diverging is the first word, it usually means take the diverging route at that signal. Advance Approach Diverging would make more sense. (Our Diverging Advance Approach is red over flashing yellow, take the diverging route and be prepared to stop at the second signal, etc).
A yellow (or flashing yellow) over green used to be Advance Approach to us. Be prepared to stop at the second signal, reducing to 40mph and, where it was in advance of 40+ mph turnouts, prepared to take the diverging route at the next turnout. Now an Advance Approach aspect is a flashing yellow, singly or in combination with red aspect(s).
Jeff
On CN, in the US, flashing yellow is advance approach. Flashing green is advance approach diverging.
CN’s Waukesha sub isn’t cab signal territory and isn’t governed by the NORAC rulebook. That’s why crews have to qualify on districts where they operate. In general a flashing aspect allows for either a minor speed upgrade compared to a non-flashing aspect (permitting limited speed instead of medium speed, for example), or it allows additional information to be conveyed without requiring additional heads as in the CN example here.
Here’s the NORAC rule which covers most of the northeast:
CAB Speed is used only in cab signal territory and only if the top (or only) head is flashing green. The rule associated with the aspect:
Rule 281a CAB SPEED
Proceed in accordance with cab signal indication. Reduce speed to not exceeding 80 MPH when Cab Speed cab signal aspect is received. Reduce speed to no exceeding Limited Speed when Approach Medium cab signal aspect is received. Trains not equipped with operative cab signals must not exceed 79 MPH.
OK, thanks much for that clarification, additional information, and reference ! [tup]
- Paul North.
Here’s a link to the CN block and interlocking signals:
http://www.blet724.org/files/CORA/cora-cn.pdf
Please go to page 11. There are a few different types of flasing green signals.
CC
CN’s rulebook is - loke the NORAC rulebook - a good example of rulebook by history. The multiple aspects for each rule show the differing heritage of CN’s chicago area lines. Here’s where local qualification really takes hold - without knowing the particular signal several indications would be plausible - even assuming only one head or flashing green on the top head only:
Rule 803 Clear
Signal 6 - Not applicable on the Waukesha Sub - apparently only applies to certain low signals on other, ex EJ&E or ex-IC subs.
Rule 807 Advance Approach diverging
Seems most likely indication well described elsewhere in this thread - note tis is an es-Soo Line signal.
Rule 823 Limited Clear
No mention of lower head, low signal only. I’m guessing ex-EJ&E lines only.
CN has different rules for some subdivisions. In Michigan they are different on the Holly sub than on the Flint sub. Also, upon reaching the tunnel yard in Port Huron heading east the Canada rules begin.
I now understand why a crew must be qualified on each territory they run. As a for-instance, a crew going from Detroit to Chicago would have to change to the Flint sub rules at Durand.
Once they get to Chicago the rules change again. The 2007 collision of the Pere Marquette with an NS freight in Chicago involved a crew member in training subject to multiple rulebooks misinterpreting a signal, calling a CSX “Slow Approach” instead of a NORAC/NS “restricting” for a red over yellow.
You’re correct. I typed it backwards. Turning at the second light is the important thing.
I haven’t been on that territory for a little while anyways. If you don’t use it you lose it.
And, sometimes one railroad will have one meaning for a particular light and another railroad will have the opposite. In the spring of 1969, I was riding the Powhatan Arrow from Cincinnati to Norfolk, and noticed the lunar white signals on both the B&O and the N&W. I asked the flagman what they meant, and he told me. I do not remember what the aspects were–but they were opposite. The engineer certainly had to know which road he was as he came into or left Cincinnati since the N&W had trackage rights on the B&O as well as on the PRR to gain access to Cincinnati Union Station.
These replies indicating that a flashing green tells the engineer to turn seem strange to me. I don’t recall ever seeing a steering wheel in a locomotive cab and I don’t recall ever seeing a crew member get down and line a route in signaled territory.
Back in the day, a Flashing Green on the NYC and PC was a Limited Clear: Proceed at limited speed through the interlocking. And our rule book classes emphasized that signals indicated the maximum speed permitted by the entire train through the next block or through the interlocking. A Medium Clear or Slow Clear was typically seen when a diverging route had been set up, but, strictly speaking, the signal indicated speed and not route.
If I recall correctly from my copy of “All About Signals”, limited speed indications were devised to take advantage of improved trackwork through interlockings, such as equilateral turnouts. Limited Clear could indicate a diverging route if the route allowed that speed.
Flashing green is what you get for a diverging route on those super-long 80 mph crossovers in few spots on the NEC.
T-That’s a joke, son. You’re supposed to laugh!
It all depends! I have a CN Great Lakes Region Employee Time Table with 2+ pages of signal indications of which six show at least one flashing green and they all had “limited” in the indication.
On the D&H where I was employed a flashing middle green was essentially a route signal interposed over a speed signalling system. Red-flashing green-red was medium clear. I recall this indication being used at only three locations. All were junctions where two tracks became one and there was a junction switch beyond the first switch in the same interlocking. A solid green in the middle meant the movement was going from double to single track through the diverging leg of the turnout at the end of double track to single track. The flashing green meant the train was going from double track to single track through the diverging leg of the turnout AND diverging at the junction switch. As the D&H did not employ any “Limited” signal indications this did not conflict with any standard books of rules.
Probably just an exception that proves the rule! Do we have you confused yet?