27-03-2015, 03:37 PM
AWS is not placed at the minimum braking point from any signal (excepting very low speed scenarios). AWS does not and cannot guarantee a SPAD will not occur. Also, a SPAD is not necessarily dangerous in itself as the TPWS philosophy of stopping the train beyond the signal demonstrates.
What do you mean by intervene? A driver has to interact with AWS at every adverse [non-green aspect] signal. If the question is why are drivers permitted to cancel AWS on approach to a red aspect; the AWS system is not intelligent at all and cannot differentate between the non-green aspects. It was designed in fifty or sixty years ago and selected over the, arguemtatively, better ATC on the Western.
All drivers, for almost every interaction with AWS, acknolwedge it correctly and stop their train in appropriate positions. Sometimes, humans make errors and override or ignore the warning (normally inadvertantly). I'd recommend reading some human factors studies to explain why humans can and do make errors, often totally illogical, especially under even slightly abnormal situations.
You could ask why drivers are still necessary when planes fly without the pilot's assistance!
J
What do you mean by intervene? A driver has to interact with AWS at every adverse [non-green aspect] signal. If the question is why are drivers permitted to cancel AWS on approach to a red aspect; the AWS system is not intelligent at all and cannot differentate between the non-green aspects. It was designed in fifty or sixty years ago and selected over the, arguemtatively, better ATC on the Western.
All drivers, for almost every interaction with AWS, acknolwedge it correctly and stop their train in appropriate positions. Sometimes, humans make errors and override or ignore the warning (normally inadvertantly). I'd recommend reading some human factors studies to explain why humans can and do make errors, often totally illogical, especially under even slightly abnormal situations.
You could ask why drivers are still necessary when planes fly without the pilot's assistance!
J
Le coureur