15-09-2017, 01:23 PM
Matt,
Am struggling to read your attempt so am going to throw some thoughts down.
Assuming a stop signal is the end of the authority and we take tripcocks, AWS and TPWS OSS as examples, none guarantee stopping at the signal. Both should stop a train within the "overlap" under normal braking conditions. All could end up as a SPAD. Think about AWS, at linespeed, let's assume 100mph, would 180m be sufficient to stop at the signal or even in the overlap? Is ATP a solution? Whilst it may improve various circumstances, equipment failing in front of the train will not necessarily prevent a SPAD or movement beyond a MA - remember, not all ATP is ETCS!
Does that mean there will be a collision? No. Remember the difference between "hazardous location or conflict" and what a SPAD or exceeding a MA actually are.
For part B apart from equipment failure, there is adhesion, driver error (accelerating after an OSS [see Dorothy's comment]), notice some of these are mentioned in your answer but i) mixes up overlap and hazard/conflict.
Am struggling to read your attempt so am going to throw some thoughts down.
Assuming a stop signal is the end of the authority and we take tripcocks, AWS and TPWS OSS as examples, none guarantee stopping at the signal. Both should stop a train within the "overlap" under normal braking conditions. All could end up as a SPAD. Think about AWS, at linespeed, let's assume 100mph, would 180m be sufficient to stop at the signal or even in the overlap? Is ATP a solution? Whilst it may improve various circumstances, equipment failing in front of the train will not necessarily prevent a SPAD or movement beyond a MA - remember, not all ATP is ETCS!
Does that mean there will be a collision? No. Remember the difference between "hazardous location or conflict" and what a SPAD or exceeding a MA actually are.
For part B apart from equipment failure, there is adhesion, driver error (accelerating after an OSS [see Dorothy's comment]), notice some of these are mentioned in your answer but i) mixes up overlap and hazard/conflict.
Le coureur