07-09-2014, 04:04 PM
A reasonable attempt for what is a tricky problem to solve. A clear set of assumptions can certainly aid the answer overall. The examiners are just looking for a demonstration that a candidate understands how to approach safety and the effects of implimenting rules, human factors etc.
I would offer three options to the examiner. For me, two isn't sufficient. The assumption list is good but some of the assumptions should be limited to specific options.
For me, there are three basic options:
1) low-risk - fully signalled moves, reduced service - capacity killer but safe!
2) medium-risk - reduced service, run down trains on the up fast, ups on the up slow - most fully signalled but a few people on the ground, reduced capacity.
3) high-risk - full service, run down trains on the up fast, ups on the up slow, keep branch open - most fully signalled but more people on the ground, very risky due to complexity of west junctions, the branch and bi-di moves (assuming branch reverses/terminates at B).
Many clues in the text and diagram about what to watch for i.e. the tunnel. That makes any non-signalled moves far more risky as do turnbacks, crossings down trains across fast and vice versa. The route between 805b and 812a being particularly hazardous under rules based signalling. It would also be worth talking about duration for clearing the blockage. Longer periods require handovers, multiple rush-hours etc.
Remember, M1 is about safety so don't get drawn into describing technical solutions. Signalled routes are safer by default. Large numbers of lineside people will put pressure on the signaller who has to control each of them individually and as a group. They won't be used to doing so and mistakes will occur. The tunnel will likely reduce the drivers' ability to spot an error and stop those on the ground from watch what the others are doing.
There certainly is a basis for an answer but as Peter states, it would be difficult to give more than a few marks.
Jerry
I would offer three options to the examiner. For me, two isn't sufficient. The assumption list is good but some of the assumptions should be limited to specific options.
For me, there are three basic options:
1) low-risk - fully signalled moves, reduced service - capacity killer but safe!
2) medium-risk - reduced service, run down trains on the up fast, ups on the up slow - most fully signalled but a few people on the ground, reduced capacity.
3) high-risk - full service, run down trains on the up fast, ups on the up slow, keep branch open - most fully signalled but more people on the ground, very risky due to complexity of west junctions, the branch and bi-di moves (assuming branch reverses/terminates at B).
Many clues in the text and diagram about what to watch for i.e. the tunnel. That makes any non-signalled moves far more risky as do turnbacks, crossings down trains across fast and vice versa. The route between 805b and 812a being particularly hazardous under rules based signalling. It would also be worth talking about duration for clearing the blockage. Longer periods require handovers, multiple rush-hours etc.
Remember, M1 is about safety so don't get drawn into describing technical solutions. Signalled routes are safer by default. Large numbers of lineside people will put pressure on the signaller who has to control each of them individually and as a group. They won't be used to doing so and mistakes will occur. The tunnel will likely reduce the drivers' ability to spot an error and stop those on the ground from watch what the others are doing.
There certainly is a basis for an answer but as Peter states, it would be difficult to give more than a few marks.
Jerry
Le coureur