Unusual MBTA Signal Progressions

Discussion relating to commuter rail, light rail, and subway operations of the MBTA.

Moderators: CRail, sery2831

Unusual MBTA Signal Progressions

Postby BostonUrbEx » Wed Sep 23, 2015 11:26 pm

Looking for anything other than Clear, Approach, Stop.

I know that some of the signals in the CPF FR to CPF HA (Lawrence to Haverhill, roughly) stretch will give out Clear, Approach Medium, Approach, Stop [& Proceed] depending on which signal is displaying Stop or Stop & Proceed.

Does the MBTA shy away from Advanced Approach?
User avatar
BostonUrbEx
 
Posts: 3603
Joined: Thu Dec 03, 2009 9:55 pm
Location: Winn to MPT 8, Boston to MPN 38, and Hat to Bank

Re: Unusual MBTA Signal Progressions

Postby 8th Notch » Thu Sep 24, 2015 12:08 am

I think the only line that uses Advance Approach as far as MBTA territory is the Worcester Main line.
8th Notch
 
Posts: 512
Joined: Fri Jan 17, 2014 1:23 pm

Re: Unusual MBTA Signal Progressions

Postby sery2831 » Thu Sep 24, 2015 12:56 am

I will have to reply to this more when I have time, but... There is no Advanced Approach on the North Side and there are a few places I think that should have this. Under normal circumstances though, it's clear, approach medium(in territory with two headed automatics), approach, stop. The new Fitchburg Route signals with two heads though go clear to approach though. Not sure why!!! Advanced Approach is used when the normal progression is too close together and in general is used as a last resort to protect a stop signal.
Moderator: MBTA Rail Operations
User avatar
sery2831
 
Posts: 5136
Joined: Fri Mar 12, 2004 2:15 pm
Location: Manchester, NH

Re: Unusual MBTA Signal Progressions

Postby MBTA F40PH-2C 1050 » Fri Sep 25, 2015 2:40 pm

8th Notch wrote:I think the only line that uses Advance Approach as far as MBTA territory is the Worcester Main line.


Advanced Approach is also used on the Amtrak Mianline...where high speed sections and short blocks are located (the Sharon stretch and down in the Warwick, RI area)
MBTA F40PH-2C 1050
 
Posts: 3498
Joined: Thu Mar 11, 2004 7:57 pm

Re: Unusual MBTA Signal Progressions

Postby BostonUrbEx » Fri Sep 25, 2015 11:23 pm

I have a good one, when going westbound on Track 1 in Lawrence. Approach (CPF AS), Restricting (CPF JK), Slow Clear (CPF FY). Going east, when diverging at CPF FY, you also have: Approach (Distant to CPF FY), Slow Approach (CPF FY). Both progressions in place due to a 10 MPH switch at CPF FY.
User avatar
BostonUrbEx
 
Posts: 3603
Joined: Thu Dec 03, 2009 9:55 pm
Location: Winn to MPT 8, Boston to MPN 38, and Hat to Bank

Re: Unusual MBTA Signal Progressions

Postby CRail » Sun Sep 27, 2015 2:36 pm

Medium Approach Mediums are typical at Salem on the eastbound just west of the tunnel and at westbound at Everett Junction. This occurs when a home signal is also the distant signal for the next interlocking (in other words, there are no distant signals between home signals. In this case the home signal for Everett Junction serves as the distant for Reading Junction).
Moderator: Massachusetts Bay Transportation Authority
Avatar:3679A (since wrecked)/3623B (now in service as 3636B).
User avatar
CRail
 
Posts: 2132
Joined: Tue May 18, 2004 8:27 am
Location: Eastie

Re: Unusual MBTA Signal Progressions

Postby BostonUrbEx » Mon Sep 28, 2015 1:59 pm

Medium Approach Medium also occurs when trains are crossing over at both CPF AS and CPF FR in Lawrence. Both switches, as far as I know (not sure on AS exactly), are good for 45+ MPH, and would normally be Limited speed. I'm rather surprised that the MBTA hasn't worked to have a non-conforming Limited Approach Limited signal.
User avatar
BostonUrbEx
 
Posts: 3603
Joined: Thu Dec 03, 2009 9:55 pm
Location: Winn to MPT 8, Boston to MPN 38, and Hat to Bank

Re: Unusual MBTA Signal Progressions

Postby ExCon90 » Mon Sep 28, 2015 3:42 pm

NORAC logic would seem to require R/*Y*/*G*, which ought to be possible--and fail-safe: if the flasher on the middle unit failed you'd have Medium Approach Limited, and if it failed on the bottom one it would be Limited Approach Medium, and if both failed you'd have what you have now. I don't know what it would cost, however. (This is one major difference from GCOR, by the way; on LA Metrolink if you're taking the siding you get Approach Diverging (Y/Y) on the distant and Diverging Clear (R/G) on the home. The fact that the next signal is another Diverging Clear is covered by the rule that Clear means proceed at maximum authorized speed, and if the timetable provides that the speed over a reversed switch at the interlocking is, say 40 mph, then Diverging Clear means proceed approaching next interlocking at 40 mph.)
ExCon90
 
Posts: 3491
Joined: Thu Sep 18, 2008 1:22 pm


Return to Massachusetts Bay Transportation Authority (MBTA)

Who is online

Users browsing this forum: No registered users and 7 guests