First Attempt

[aylso]

Hi,

This is my first time to site in M3.  I tried one of the route in Q1.
It is much appreciated if anyone may give comment.

Alan

[PJW]

Hi,

This is my first time to site in M3.  I tried one of the route in Q1.
It is much appreciated if anyone may give comment.

Alan

Sorry for not responding earlier- I have been busy on several fronts.
Indeed I actually asked Reuben to look at this for me and he responded  to me by email so I am posting his response:

Feedback on Route 103A(M) control table-
PLEASE ALSO SEE ATTACHED
 
Points free to go or Release
 
This pair of columns should list all point numbers relevant to the route
The points should be:
·        Directly in the route
·        Within the overlap (except for swinging overlaps with multiple options)
·        Providing flank protection to the route
·        (Without A/B end references, because it’s only dealing with the “whole point” commands issued by the interlocking)
 
There will be a strong similarity between the above columns and the later group of columns “Points Called, Locked and Detected” -  essentially the entries in the latter should mirror those in the first group, with the addition of listing all detection mechanisms (ie A and B ends)
 
The reason for the apparent duplication is that the first “free to go” columns describe how the route tests points available (not locked by another route) before it is allowed to set, whereas the second group “called and detected) confirms that the rails have moved to provide a safe wheeled path, before the signal is allowed to show proceed.
 
You seem to have a confusion over these columns, noticeably being averse to any item being mirrored in both – I’m not sure why? I also think you’ve an issue with the “normal” lie. This is shown by the solid line (usually also straight) , and reverse by the broken line (usually divergent). Noticeably, both 116 and 122 points both have normal defined as the “divergent” alignment, and you’ve got these both wrong.
 
Opposing Route Locking
 
The idea here is that you must not let the route set if it would come into conflict with an already set route. In practice, most of the potential conflicts are resolved by the points, referenced in the previous group of columns, already being locked in the counter position.
 
For this reason, the following routes you have referenced are NOT required, because they’re already done by the points inherently:
 
152 A, C& D routes
145 all routes
141
154 C, D routes
156 B C routes
147 all routes
143 all routes
 
The routes we do have to consider are:
Other from same signal along same path – 103A©
Directly opposing – 156A(S), 164B(S)
Indirectly opposing 152A, 154A
Preset shunt routes – 105A(s)
 
Tracks clear
 
You’re correct to consider foul track circuits FA and CJ; however these will both be inherently conditioned-out by points 109N and 113R respectively.
 
Aspect sequence
 
Notice that exit signal 157 is 4 aspect
 
Approach Locking
Being a signal with automatic working, this would be a good candidate to provide comprehensive approach locking (tracks clear EF to EB), and it’s very easy for once!
The second release condition should also require EF still occupied.
The timer is too short at 30s; 120 or 180 would be more appropriate for a main class route
 
Summary
You’ve successfully cherry-picked some easy stuff and got it right. However there are some fundamental problems with points and opposing routes; an answer of this standard would not expect to pass, sorry!

[aylso]

Thanks PJW for your opinion.

[lokko]

Dear PJW and all,

Attached is my attempt to the 2015 exam question.
I would like to ask for Point CT of 121.
Is it appropriate to include also 157A(M) in the "Points called by routes" ? There are several consideration in my mind.

(1) Set 121 to reverse to avoid train approach 122 accidentally when 157A(M) is set
(2) CP consideration
(3) While setting 121R will essentially reduce the availability of 161OL

Thanks