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Re: Super bad BNSF wreck east of Amarillo
Author: ble20
Date: 06-29-2016 - 12:10
An expert Wrote:
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> And yet, I am positive it is not a better way to
> control trains. The fact is, GPS is NOT the end
> all, be all when it comes to position, navigation
> and timing. It is a great technology, but it is
> not what the general public thinks it is. The
> fact is, the military - who developed the
> technology - is constantly looking at ways to
> supplement it and in its control systems, only
> uses it as a secondary control source.
> Additionally, there are limitations and
> shortcomings which are inherent in using GPS as a
> PNT method. For example, when a train is moving
> at 79 mph, it is only accurate to around 12-15 ft
> - accurate enough for single track operation, but
> not enough for multi-track operation. In order to
> make it work, you must add infrastructure and
> implement a dGPS system, meaning there are towers
> providing known position data to increase accuracy
> at speed (and these towers ideally must be placed
> sufficiently away from the right of way to provide
> the necessary increase in resolution needed).
> Next, it introduces a security issue, given that
> train movements are critical to the national
> economy and passenger traffic is placed at risk. I
> have seen little in discussions about PTC which
> address the security implications of using a radio
> based control system (including GPS). The US
> military spends large amounts of money to
> counteract these security threats, yet the PTC
> implementations I've seen do not seem to
> adequately consider them. If I were an executive
> for a railroad, I would balk at the cost of PTC
> and the necessary security countermeasures for
> electronic warfare. They are nuanced and mostly
> classified - something the rail industry clearly
> does not want to deal with. Additionally, the
> improvements in GPS-based train control systems
> only provide a marginal improvement in performance
> over traditional track-circuit based systems.
> There are other issues as well. GPS is great - I
> use it personally all the time and deal with it
> professionally always. So, after having worked
> closely with navigational systems since grad
> school, I am definitely not convinced it is better
> for rail applications. Sure, its cool and sexy,
> but better - I doubt it.
According to my friends in the Comm. Dept., you are correct relative to the granularity that OTS GPS can provide. Some of the railroads have used LADAR in attempt to better define the fixed railroad and naturally occurring objects along the ROW and thus make PTC a bit more accurate. While the crash at Panhandle may/may not have been totally prevented by PTC intervention is anybody's guess, it is being said that the resolution provided by PTC as now being deployed might have tripped an emergency application of the brakes in sufficient time to provide this story with a different outcome.
But we have to remember that only the NTSB and news media (plus a few of the "unwashed masses" out there) have deemed PTC to be the "be all, end all" application to prevent "derailments and crashes." The rest of us whose lives will be affected don't feel so secure in that belief . . .
-------------------------------------------------------
> And yet, I am positive it is not a better way to
> control trains. The fact is, GPS is NOT the end
> all, be all when it comes to position, navigation
> and timing. It is a great technology, but it is
> not what the general public thinks it is. The
> fact is, the military - who developed the
> technology - is constantly looking at ways to
> supplement it and in its control systems, only
> uses it as a secondary control source.
> Additionally, there are limitations and
> shortcomings which are inherent in using GPS as a
> PNT method. For example, when a train is moving
> at 79 mph, it is only accurate to around 12-15 ft
> - accurate enough for single track operation, but
> not enough for multi-track operation. In order to
> make it work, you must add infrastructure and
> implement a dGPS system, meaning there are towers
> providing known position data to increase accuracy
> at speed (and these towers ideally must be placed
> sufficiently away from the right of way to provide
> the necessary increase in resolution needed).
> Next, it introduces a security issue, given that
> train movements are critical to the national
> economy and passenger traffic is placed at risk. I
> have seen little in discussions about PTC which
> address the security implications of using a radio
> based control system (including GPS). The US
> military spends large amounts of money to
> counteract these security threats, yet the PTC
> implementations I've seen do not seem to
> adequately consider them. If I were an executive
> for a railroad, I would balk at the cost of PTC
> and the necessary security countermeasures for
> electronic warfare. They are nuanced and mostly
> classified - something the rail industry clearly
> does not want to deal with. Additionally, the
> improvements in GPS-based train control systems
> only provide a marginal improvement in performance
> over traditional track-circuit based systems.
> There are other issues as well. GPS is great - I
> use it personally all the time and deal with it
> professionally always. So, after having worked
> closely with navigational systems since grad
> school, I am definitely not convinced it is better
> for rail applications. Sure, its cool and sexy,
> but better - I doubt it.
According to my friends in the Comm. Dept., you are correct relative to the granularity that OTS GPS can provide. Some of the railroads have used LADAR in attempt to better define the fixed railroad and naturally occurring objects along the ROW and thus make PTC a bit more accurate. While the crash at Panhandle may/may not have been totally prevented by PTC intervention is anybody's guess, it is being said that the resolution provided by PTC as now being deployed might have tripped an emergency application of the brakes in sufficient time to provide this story with a different outcome.
But we have to remember that only the NTSB and news media (plus a few of the "unwashed masses" out there) have deemed PTC to be the "be all, end all" application to prevent "derailments and crashes." The rest of us whose lives will be affected don't feel so secure in that belief . . .
