Everyone is missing the obvious in the Metrolink wreck.

[Expresslane]

Hey zardoz     You seem to not like conductors.

Not true.  I just do not like someone who's behavior puts my (as well as others) life at risk.

EVERYONE in the operating department of any class 1 railroad has fallen asleep on duty at one time or another (but only the honest ones admit it).  I certainly have. And when I did, I was not happy with myself, for I knew I put my life, as well as my conductor's life, as well as the life of everyone who lived near the tracks, at risk.

    Hey thanks and good answer.

[oltmannd]

As a counter-example, what about New York City subway trains or PATH commuter trains?  During rush hours some trains have about 500 passengers and run at intervals of about a minute.  That's a huge responsibility.  They're remarkably safe, and I don't hear anyone saying safety suffers for lacking a second person in the cab -- remarkable in a city filled with so many people quick to criticise.  One thing not mentioned is that most commuter operations run on a thin edge, requiring a second person would probably make most of them economically unviable.

Subway systems are equiped with fail safe devises that will stop train in the advent of a speed limit or signal aspect violation.  As I said before you are comparing apples to oranges here. 

These are mostly reactive, not predictive.  This wreck probably would have occurred anyway with reactive system.  That is, the brakes wouldn't apply until after the train passes the stop signal.  At 40 mph, the train would have rolled thru the switch before stopping. 

[eastside]

As a counter-example, what about New York City subway trains or PATH commuter trains?  During rush hours some trains have about 500 passengers and run at intervals of about a minute.  That's a huge responsibility.  They're remarkably safe, and I don't hear anyone saying safety suffers for lacking a second person in the cab -- remarkable in a city filled with so many people quick to criticise.  One thing not mentioned is that most commuter operations run on a thin edge, requiring a second person would probably make most of them economically unviable.

Subway systems are equiped with fail safe devises that will stop train in the advent of a speed limit or signal aspect violation.  As I said before you are comparing apples to oranges here. 

I'm really speaking about all commuter trains in Chicago and NYC including Metra and Metro North.   They don't have such systems in place.  The triple track on the west side of Chicago, for example, extensively runs both freight and passenger as do many routes in Chicago.

[erikem]

Here's how it works.  The dispatcher initiates an authority for main track movement.  The dispatching computer runs a conflict check, and if the requested authority has no conflicts, it grants the dispatcher the ability to transmit the authority to the train.  The dispatching server transmits the authority to the PTC server (which is in the same rack), and the PTC server transmits the authority to the locomotive-based PTC computer.  The PTC computer on the locomotive is listening at all times for incoming signals.  When the computer on the locomotive receives a new authority, it runs its own conflict check ("Am I activated?  Am I operating properly?  Does this authority have any conflicts with existing authorities stored in my memory for my train and any other train I know about?")  If there are no conflicts, it accepts the authority and transmits back to the PTC server its acceptance.  When the PTC server accepts the receipt, it transmits back its acceptance and when the locomotive receives this final handshake, the authority is now valid for the train.  The PTC server is meanwhile locked-up and can create no new authorities (but all of this takes a matter of a few seconds at most) in order that no conflicts can be created during the handshake.

Presumably the servers at least a couple of steps up from an e-machines rack mount box running Windows Vista home edition... Probably the most straightforward way of getting reasonably decent hardware would be to specify NEBS certified servers. Attention also needs to be paid to proper redundancy and diversity in communications and power routing (nothing too far out of the ordinary for someone used to setting up data centers) - from what I've heard/read, getting five nines availability requires a lot of attention to detail - you did point out that the protocols have a lot of fail-safes built in.

 

Your other concern was whether the railroad would have schedule and efficiency loss if communications fail.  Different manufacturers have different solutions, but one common solution is to have a primary pathway via VHF radio, a secondary pathway through hot-standby VHF radio, and a tertiary pathway through Iridium satellite.  The locomotive polls the primary system first (it's the cheapest to operate.  The secondary is automatic within the VHF system and not visible to the locomotive.  If VHF doesn't respond the locomotive polls the Iridium satellite in geostationary orbit, and usually the locomotive can "see" five or more satellites at once.  Each of these systems is built to at least five-nines reliability (but usually seven-nines reliability) meaning that the total probable downtime per year when there is no communication with the locomotive is a few seconds.  During those few seconds the system remains fail-safe.

Minor nitpick: Iridium is in low earth orbit (LEO) and requires (IIRC) a constellation of 66 satellites to provide coverage. This has three very distinct advantages over geosynchronous (GEO): first being that coverage at high latitudes is much better (even available at the poles); second is that the path loss is approx 20dB less at LEO than GEO, thus requiring less transmitter power; third is the latency is much shorter, maybe a few hundreths of a second as opposed to a few tenths of a second.

[Anonymous]

In responding to a prior post I would like to add that having a second pair of eyes in the cab is exactly what is need in commuter train service.

Hmm. You're in commuter train service yourself?

Since these trains run on tight scheduals that run in a predictable manner each day, engineers run the risk of getting into the mind set that they will get the same signal aspets at the same locations every day.  I suspect that the Metrolink engineer assumed he had a light at that Control Point because he almost never got held there by the dispatcher in the past.  Had a second person been in that cab to call attention to the unusual signal aspect the accident would never have happend.

Assuming of course that the second person was paying attention. Big assumption, based on my experience.

Mark.

 

 1.  Actually I am a frieght train conductor who works in Commuter train territory, so I do know what kinds of things Commutrer train crews confront.

2.  The rule book says that both members of a train crew are responsible for the safe opperation of their train.  The rule book also states that each crew member has the responsibility to remind their co-workers to follow the rules, including the one that states that employees must be alert and atentive while on the job.  Clearly Mark, if you have had trouble with inatentive crewmembers it is your fault for not correcting that situation. 

[Anonymous]

As a counter-example, what about New York City subway trains or PATH commuter trains?  During rush hours some trains have about 500 passengers and run at intervals of about a minute.  That's a huge responsibility.  They're remarkably safe, and I don't hear anyone saying safety suffers for lacking a second person in the cab -- remarkable in a city filled with so many people quick to criticise.  One thing not mentioned is that most commuter operations run on a thin edge, requiring a second person would probably make most of them economically unviable.

Subway systems are equiped with fail safe devises that will stop train in the advent of a speed limit or signal aspect violation.  As I said before you are comparing apples to oranges here. 

[ndbprr]

I don't know of any subways that have crossings at grade; that many trespassers; heavy equipment getting foul of the tracks; washouts; floods; landslides; trees on the tracks; sun kinks; snow drifts; blizzards; signals hard to see because of snow, fog, and sunlight; farm animals running loose on the right of way; obscured site lines because of rampant vegetation growth; Rule 42s; slow orders;

West side of Chicago crosing several main streets.

[eastside]

As a counter-example, what about New York City subway trains or PATH commuter trains?  During rush hours some trains have about 500 passengers and run at intervals of about a minute.  That's a huge responsibility.  They're remarkably safe, and I don't hear anyone saying safety suffers for lacking a second person in the cab -- remarkable in a city filled with so many people quick to criticise.  One thing not mentioned is that most commuter operations run on a thin edge, requiring a second person would probably make most of them economically unviable.

I don't know of any subways that have crossings at grade; that many trespassers; heavy equipment getting foul of the tracks; washouts; floods; landslides; trees on the tracks; sun kinks; snow drifts; blizzards; signals hard to see because of snow, fog, and sunlight; farm animals running loose on the right of way; obscured site lines because of rampant vegetation growth; Rule 42s; slow orders; freight trains going by; railway equipment on or near the track; manual derails to set; etc.

Tokyo has grade crossings and they're about as busy as it gets.  Chicago also has some.  I think subway train drivers have plenty of hazards to look out for such as people wandering on the tracks, over-, under-shooting platforms, etc.  AFAIK snow drifts, farm animals, etc. weren't factors in the L.A. crash.

I'm not positive but isn't there some form of fail safe mechanism if a subway train goes by a stop signal or exceeds a set speed limit?

There's just way too much going on in the head end for just one person on a busy rail line especially in an urban area. Multi track mixed with single track aggravates the situation.

It's not viable to have an extra employee in the head end when it conflicts with the bottom line. Remember, the new age mantra is 'Profit Before Safety'. Shareholders come first. Also the commuter service in question is operated by contractors and it's their business to make money, not provide a safe working environment for their employees or a safe environment for the public both on and off the train. Contractors will cut corners left and right to save expenditures on the maintenance of the infrastructure and maintaining adequate personal.

In the long run contractors cost more.

MTA (NY city subway system), Metro North, PATH are all public agencies and aren't run for a profit.  My guess is that they carry more passengers than all of the rest of the North America, yet fatal accidents to riders are extremely rare. Pretty remarkable to me.  AFAIK, none employ contractors for train operations.  Nevertheless, they have to live in the real world of budgets (minimizing the cost to taxpayers).  I've never heard a call for a second person in the cab on any of these lines.  So far, I haven't seen any compellingly persuasive argument in this thread that Metrolink is so different from Chicago or NYC that it should have a second person and the other cities doing fine without one for over a century.

[marknewton]

So you mean to tell me that you have never had an experience where someone riding with you didn't point out or remind you about something that you may have missed.  I am willing to bet you have had such things happen to you but the occasions were so minor that you have forgoten all about them.  Remember everyone, the history books are full of major tragedies that could have been avoided had one single factor been changed.  Had a second man been in that cab I doubt he would have kept silent while the train was aproaching a stop signal without at the very least making some sort of comment.

Quite possibly, but as I don't have any first-hand experience of running US commuter trains, I wouldn't like to say with certainty. As I wrote earlier, I think each case should be considered on its merits. I've never run loco-hauled commuter trains, only EMUs and DMUs, all of which are equipped with deadman control, vigilance control - alerters - and trip gear - automatic train stops.

If you don't acknowledge the vigo, or don't operate a nominated control during the timing cycle, the system will activate, and you will eventually get a penalty if you don't respond. In our case, the vigo will make an emergency application and take the power away, and the train will stop. If you spad, the trip gear operates, the brake pipe is opened, power is shut off, and the train will stop. In either case, getting the air back requires the co-operation of the guard - conductor - before you can proceed. So as I wrote before, I can't see any advantage in two-man crews for our operation. But as I said, horses for courses. You may well be right about a second person where Metrolink is concerned.

Cheers,

Mark.

[marknewton]

In responding to a prior post I would like to add that having a second pair of eyes in the cab is exactly what is need in commuter train service.

Hmm. You're in commuter train service yourself?

Since these trains run on tight scheduals that run in a predictable manner each day, engineers run the risk of getting into the mind set that they will get the same signal aspets at the same locations every day.  I suspect that the Metrolink engineer assumed he had a light at that Control Point because he almost never got held there by the dispatcher in the past.  Had a second person been in that cab to call attention to the unusual signal aspect the accident would never have happend.

Assuming of course that the second person was paying attention. Big assumption, based on my experience.

Mark.

[marknewton]

Of course in the EU where the railroads have been subsidised by Socialist infrastructure programs I am willing to bet all locomotives and rail lines have some sort of Positive Train Seperation system already in place. 

You'd lose that bet. Not all locos or lines in Europe have PTS, nor do all railways in Europe receive subsidies from "socialist infrastructure programs"...

Mark.

[CliqueofOne]

As a counter-example, what about New York City subway trains or PATH commuter trains?  During rush hours some trains have about 500 passengers and run at intervals of about a minute.  That's a huge responsibility.  They're remarkably safe, and I don't hear anyone saying safety suffers for lacking a second person in the cab -- remarkable in a city filled with so many people quick to criticise.  One thing not mentioned is that most commuter operations run on a thin edge, requiring a second person would probably make most of them economically unviable.

I don't know of any subways that have crossings at grade; that many trespassers; heavy equipment getting foul of the tracks; washouts; floods; landslides; trees on the tracks; sun kinks; snow drifts; blizzards; signals hard to see because of snow, fog, and sunlight; farm animals running loose on the right of way; obscured site lines because of rampant vegetation growth; Rule 42s; slow orders; freight trains going by; railway equipment on or near the track; manual derails to set; etc.

I'm not positive but isn't there some form of fail safe mechanism if a subway train goes by a stop signal or exceeds a set speed limit?

There's just way too much going on in the head end for just one person on a busy rail line especially in an urban area. Multi track mixed with single track aggravates the situation.

It's not viable to have an extra employee in the head end when it conflicts with the bottom line. Remember, the new age mantra is 'Profit Before Safety'. Shareholders come first. Also the commuter service in question is operated by contractors and it's their business to make money, not provide a safe working environment for their employees or a safe environment for the public both on and off the train. Contractors will cut corners left and right to save expenditures on the maintenance of the infrastructure and maintaining adequate personal.

In the long run contractors cost more.

[eastside]

As a counter-example, what about New York City subway trains or PATH commuter trains?  During rush hours some trains have about 500 passengers and run at intervals of about a minute.  That's a huge responsibility.  They're remarkably safe, and I don't hear anyone saying safety suffers for lacking a second person in the cab -- remarkable in a city filled with so many people quick to criticise.  One thing not mentioned is that most commuter operations run on a thin edge, requiring a second person would probably make most of them economically unviable.

[RRKen]

Two lines of thinking.   First, and most important is the persons ability to maintain focus on his job.    Situational awareness.    I dont have an issue with a single person in the cab of short run/time trains.   There are a lot of outstanding examples out there of safe operations.  

Next, PTC.   As an engineer who has run with ATC, I say, bring on PTC.   It will be far better than ATC could ever hope, and allow more fluid operations.   And yes, far safer in situations where short run/time commuters come into play.   

Once familiar with a line segment, you know where all the signals are, and expect them, just like you do at grade crossings, station stops, and so on.   If you have the radio on,  you hear other potential conflicting moves  happening.  So it is not as if you are running blind.  

[Anonymous]

In responding to a prior post I would like to add that having a second pair of eyes in the cab is exactly what is need in commuter train service.  Since these trains run on tight scheduals that run in a predictable manner each day, engineers run the risk of getting into the mind set that they will get the same signal aspets at the same locations every day.  I suspect that the Metrolink engineer assumed he had a light at that Control Point because he almost never got held there by the dispatcher in the past.  Had a second person been in that cab to call attention to the unusual signal aspect the accident would never have happend.

[Anonymous]

Why hasn't anyone pointed out the fact that having passenger train engineers working alone in a locomotive cab is a recipe for disaster?

Well, I'm not sure if that is true.

In the EU, most trains - freight or passenger - only have the engineer in the cab. Freights normally don't even have a conductor. Yet very few accidents happen that can be traced back to grave human error preventable by adding an extra crew member.

Of course in the EU where the railroads have been subsidised by Socialist infrastructure programs I am willing to bet all locomotives and rail lines have some sort of Positive Train Seperation system already in place.  The railroads in North America had systems like this in the past, we called it ATS (Automatic Train Stop)  but as the fortunes of the railroad industry saged between 1950-1990 most of these safety systems were ripped out to cut maintenance costs.  It would cost a fortune and take years to re-install an up to date Positive Train Control system today, an extra pair of eyes on the otherhand could be placed in all passenger train cabs within a year and cost only a fraction of PTS technology.

[Anonymous]

Why hasn't anyone pointed out the fact that having passenger train engineers working alone in a locomotive cab is a recipe for disaster?  I know from personal experience that having a second person in a locomotive cab can prevent accidents, as a frieght train conductor I have intervened on several occasions to prevent an engineer from making a mistake. 

No doubt that is true; however, I've lost count as to how many times I've had to wake up the conductor so he could go perform his duties.

....Have there been occasions were I felt that I may have just prevented an accident?  YES!!!

See above.

....After all, Commercial Airliners fly with both a Pilot and Co-Pilot in the cockpit, why should passenger trains be any different? 

Well, for one, if the engineer gets sick, he can stop his train just about anywhere he's not blocking a crossing and wait for a replacement--not quite so easy at 35,000'.

Additionally, I disagree that having two persons in the cab is the answer.  I've had many occasions where the constant chatter from a motormouth was so distracting it was difficult to concentrate.  And for the short runs of passenger service, cab monotony should not be that much of an issue--it's not like they're running at 3am after being on duty for 10 hours after getting called out on your rest.

On the other hand I have worked with some engineers who preffer working with "chaterbox" conductors because it helps them stay awake and alert. 

[Anonymous]

Hey zardoz     You seem to not like conductors.

Not true.  I just do not like someone who's behavior puts my (as well as others) life at risk.

EVERYONE in the operating department of any class 1 railroad has fallen asleep on duty at one time or another (but only the honest ones admit it).  I certainly have. And when I did, I was not happy with myself, for I knew I put my life, as well as my conductor's life, as well as the life of everyone who lived near the tracks, at risk.

I think there is a good case to be made for having alertors installed to keep conductors awake as well.  Here is an idea, how about a system were both the conductor and engineer both have to press a button at the same time to shut off the alarm?  I am willing to bet that that would be cheeper than installing a PTS system on an entire railroad system. 

[Anonymous]

Why hasn't anyone pointed out the fact that having passenger train engineers working alone in a locomotive cab is a recipe for disaster?  I know from personal experience that having a second person in a locomotive cab can prevent accidents, as a frieght train conductor I have intervened on several occasions to prevent an engineer from making a mistake. 

And I know from personal experience that having others in the cab can be more of a hindrance than a help.
I was working a train once with three driver trainees and an instructor up the front with me, and we all missed a particular signal...

So I don't think that one-man operation is automatically a recipe for disaster, each situation needs to be considered on its merits. Our suburban and interurban EMUs are all equipped with deadman and task-based vigilance control, so for us having a second person in the cab would offer no real benefit.

Cheers,

Mark.

Hey Mark,

So you mean to tell me that you have never had an experience where someone riding with you didn't point out or remind you about something that you may have missed.  I am willing to bet you have had such things happen to you but the occasions were so minor that you have forgoten all about them.  Remember everyone, the history books are full of major tragedies that could have been avoided had one single factor been changed.  Had a second man been in that cab I doubt he would have kept silent while the train was aproaching a stop signal without at the very least making some sort of comment.

[zardoz]

Hey zardoz     You seem to not like conductors.

Not true.  I just do not like someone who's behavior puts my (as well as others) life at risk.

EVERYONE in the operating department of any class 1 railroad has fallen asleep on duty at one time or another (but only the honest ones admit it).  I certainly have. And when I did, I was not happy with myself, for I knew I put my life, as well as my conductor's life, as well as the life of everyone who lived near the tracks, at risk.

[Anonymous]

Why hasn't anyone pointed out the fact that having passenger train engineers working alone in a locomotive cab is a recipe for disaster? 

There's a reason why many states ban teens from driving with other teens in the car - they aren't paying attention to the road.

Who's to say that the two people in the cab might not get into a spirited discussion of sports, politics, what-have-you?  Are they paying attention to the road?  Not if they're trying to make their point!

There's a reason why airport shuttle trains don't have collisions.  None of those that I've seen can - they either run alone or on separate tracks.  The one I've seen that had two trains running on a shared track ran on the same drive cable.  Only a broken cable could possibly allow them to be in the same place at the same time. 

 

There is a big difference between airport shuttle systems that are designed for automated operation and single track railroad lines operating with both frieght and Passenger trains of three different carriers (Union Pacific, Amtrak, and Metrolink).  

As for having spirited discussions while not watching were they are going well I supose that is possible but I believe that profissional railroaders would put aside their differences when it comes to calling out signals. 

[Anonymous]

Hey Ulrich, 

I think the stakes are much higher when a train engineer screws up than when a single truck driver or crane operator makes a mistake.  Your knee jerk reaction that if engineers need a second pair of eyes to help do their job then everyone else will be entitled to the same "budy-team" system is a non-sequitur. 

PS:  A non-sequitur is an inference that does not follow from the premises. 

[Expresslane]

Why hasn't anyone pointed out the fact that having passenger train engineers working alone in a locomotive cab is a recipe for disaster?  I know from personal experience that having a second person in a locomotive cab can prevent accidents, as a frieght train conductor I have intervened on several occasions to prevent an engineer from making a mistake. 

No doubt that is true; however, I've lost count as to how many times I've had to wake up the conductor so he could go perform his duties.

....Have there been occasions were I felt that I may have just prevented an accident?  YES!!!

See above.

....After all, Commercial Airliners fly with both a Pilot and Co-Pilot in the cockpit, why should passenger trains be any different? 

Well, for one, if the engineer gets sick, he can stop his train just about anywhere he's not blocking a crossing and wait for a replacement--not quite so easy at 35,000'.

Additionally, I disagree that having two persons in the cab is the answer.  I've had many occasions where the constant chatter from a motormouth was so distracting it was difficult to concentrate.  And for the short runs of passenger service, cab monotony should not be that much of an issue--it's not like they're running at 3am after being on duty for 10 hours after getting called out on your rest.

  Hey zardoz     You seem to not like conductors.Back in my time on your former employer as brakeman I had to help keep the engineer awake. The cab was too noisy to be able to talk with the engineer. Hey no one is perfect and I know more than once my head would bounce off the window as I fell asleep but not often. When you worked commuter trains there was two in the cab. Did one of you sleep and the other ran the train? Seems to me if they are going to have passenger and frieght trains running together on a single track territory they would have two engineers or engineer and conuctor in the cab for safety.

[Railway Man]

Correct ILS CAT III is used for autoland not GPS however GPS can now be used for the approach phase and gives a much more reliable and predicable track for intercepting the initial approach fixes but does not control altitude. Then ILS takes over. My concern with PTC is the loss of signal by the radio links. Terrain interferrence (whatever type) may cause unwanted stops and on a grades can plug a RR. 

Doesn't work like that.  There's no requirement for a continuous signal.  In fact, the central server may only poll the train as infrequently as once every minute in order to cut down on bandwidth cost.  And, there's triple redundancy through three different communication pathways.

Here's how it works.  The dispatcher initiates an authority for main track movement.  The dispatching computer runs a conflict check, and if the requested authority has no conflicts, it grants the dispatcher the ability to transmit the authority to the train.  The dispatching server transmits the authority to the PTC server (which is in the same rack), and the PTC server transmits the authority to the locomotive-based PTC computer.  The PTC computer on the locomotive is listening at all times for incoming signals.  When the computer on the locomotive receives a new authority, it runs its own conflict check ("Am I activated?  Am I operating properly?  Does this authority have any conflicts with existing authorities stored in my memory for my train and any other train I know about?")  If there are no conflicts, it accepts the authority and transmits back to the PTC server its acceptance.  When the PTC server accepts the receipt, it transmits back its acceptance and when the locomotive receives this final handshake, the authority is now valid for the train.  The PTC server is meanwhile locked-up and can create no new authorities (but all of this takes a matter of a few seconds at most) in order that no conflicts can be created during the handshake.

Now the train has an authority.  That authority has specific geographic limits.  No authority can be granted within the train's authority without modifying the train's authority, and the train won't accept a new authority or a modified authority unless it is safe to do so.  (This is just like knocking down a signal and running time.)  The point is that communication is fail-safe; if it fails the system cannot run trains into each other.  Everything stops.

Your other concern was whether the railroad would have schedule and efficiency loss if communications fail.  Different manufacturers have different solutions, but one common solution is to have a primary pathway via VHF radio, a secondary pathway through hot-standby VHF radio, and a tertiary pathway through Iridium satellite.  The locomotive polls the primary system first (it's the cheapest to operate.  The secondary is automatic within the VHF system and not visible to the locomotive.  If VHF doesn't respond the locomotive polls the Iridium satellite in geostationary orbit, and usually the locomotive can "see" five or more satellites at once.  Each of these systems is built to at least five-nines reliability (but usually seven-nines reliability) meaning that the total probable downtime per year when there is no communication with the locomotive is a few seconds.  During those few seconds the system remains fail-safe.

RWM

[Ulrich]

Yes...expecting one well paid man to do his job properly without supervision is a bit much. But don't tell that to the trucking industry...bus industry..and the construction industry or they will need two people on every truck, bus, crane and dozer..

[blue streak 1]

Correct ILS CAT III is used for autoland not GPS however GPS can now be used for the approach phase and gives a much more reliable and predicable track for intercepting the initial approach fixes but does not control altitude. Then ILS takes over. My concern with PTC is the loss of signal by the radio links. Terrain interferrence (whatever type) may cause unwanted stops and on a grades can plug a RR. 

[ndbprr]

You misunderstood if you thought I said planes were landed through the use of GPS.  What I said was that computers can land planes now and that GPs could track train location.

[oltmannd]

There was an infamous wreck years ago in Cleveland where a freight train went through a stop signal protecting a drawbridge and wrecked on the counterweight. Cleaned the carbody right off the frame.  I remember seeing a picture in Trains years ago.  I seem to remember that there were 5 guys in the cab.  John Kneiling has some sort of cynical comment related to safety vs. crew size....

There were two guys in the cab at Chase Md., too, although there were confounding factors.

[CSSHEGEWISCH]

ndbprr: GPS is not used for auto-land of aircraft. There is a precise signal that is usually broadcast from the far end of the runway you are landing on call CATEGORY III auto land. Freq band just above the FM band. GPS absolutely only can offer a decision height of 200 - 250 ft (some locations) then the landing is manual.

Do you mean ILS instead of GPS?

[blue streak 1]

ndbprr: GPS is not used for auto-land of aircraft. There is a precise signal that is usually broadcast from the far end of the runway you are landing on call CATEGORY III auto land. Freq band just above the FM band. GPS absolutely only can offer a decision height of 200 - 250 ft (some locations) then the landing is manual.