Mutant validation



  • So, in the system I work on at the RR, we have quite a few forms that users (train dispatchers, usually) fill out to do various and sundry things; among them, issuing something called a 'track and time' authority over a certain piece of the railroad (so that somebody can go out and inspect that track for defects, for instance). The track and time form requires you to name the endpoints of this authority, and it does so by asking for a control point (a place where there are some switches, signals, and stuff that can be used by the dispatcher to reroute trains) and a track 'qualifier' (a name really, like Track One, or the Pork and Beans Lead). You punch in the various things it needs, hit Create, read some stuff off on the radio to who asked you for it to start with, get a confirmation back, and hit the Confirm button. Right?

    Well, we found a spot recently where the system changes the name of the track you're applying the track and time to at one end when you hit Create, and then proceeds to barf an error because it can't find any way to get from one end of the track and time to the other. Why, oh why, would form validation code create an invalid condition?


  • Discourse touched me in a no-no place

    I don't know, but I've seen a codebase that does that sort of horror because someone decided to mutate the validation code into a generic tree visitor without changing any of the class names or documentation.

    Nice…



  • @tarunik said:

    I work on at the RR

    I've been working on the railroad, all the live-long day.

    Filed under: Sorry, I couldn't resist.



  • @tarunik said:

    Well, we found a spot recently where the system changes the name of the track you're applying the track and time to at one end when you hit Create, and then proceeds to barf an error because it can't find any way to get from one end of the track and time to the other.

    At least it generates an error. Generating a valid track and time with the wrong track could get people killed.



  • Hey, that sounds like my company. No wait, entering invalid data just makes it looks like the form wasn't submitted.



  • @HardwareGeek said:

    At least it generates an error. Generating a valid track and time with the wrong track could get people killed.

    Yeah, that's the only silver lining to this cloud. I'd rather not rely on the error handling of a system that behaves this flaky to stand between me and a ten thousand ton train barging in because it was 4AM and the dispatcher didn't notice the T&T was on the wrong track in the preview function, though!



  • @tarunik said:

    a ten thousand ton train barging in because it was 4AM and the dispatcher didn't notice the T&T was on the wrong track in the preview function, though!

    Reminds me of my glory days playing Transport Tycoon.



  • So this is why so many people get hit by trains? (I have it on good authority that there are a lot more train hits than you know about)



  • No, most of the folks who get hit are [s]trespassers[/s]idiots. Besides, we aren't close to going live with this yet (thank heavens!)



  • This post is deleted!


  • @tarunik said:

    No, most of the folks who get hit are [s]trespassers[/s]idiots.

    Yes, but that would still be true even if you were just aiming trains at everyone you could see.



  • @Scarlet_Manuka said:

    if you were just aiming trains at everyone you could see

    To be fair, if you don't run away when you see tracks being laid towards your position, maybe you deserve to be hit by a train.


    Filed under: unless you mean aiming with a catapult


  • Discourse touched me in a no-no place

    @Maciejasjmj said:

    To be fair, if you don't run away when you see tracks being laid towards your position, maybe you deserve to be hit by a train.

    Not far from where I lived in South Carolina, a woman stopped on a set of tracks in the middle of the night and started yapping on her cell, talking to a friend to try to figure out where she was. A cop saw her and argued with her for several minutes, trying to get her to move. She finally got out of her car, walked about ten feet away, changed her mind, headed back to her car, and that's when the train for which the signal was ringing for about a minute pancaked her car. I saw the video--it was pretty entertaining.

    To be minimally fair to her, the geometry of the intersection was a bit odd, so she probably thought she was off the tracks. It was basically a T that had a track right past the intersection (I mean tens of feet--I've been past there hundreds of times) and the road turned 90 degrees a few feet past the railroad track: pretty poor layout.



  • @FrostCat said:

    Not far from where I lived in South Carolina, a woman stopped on a set of tracks in the middle of the night and started yapping on her cell, talking to a friend to try to figure out where she was. A cop saw her and argued with her for several minutes, trying to get her to move. She finally got out of her car, walked about ten feet away, changed her mind, headed back to her car, and that's when the train for which the signal was ringing for about a minute pancaked her car. I saw the video--it was pretty entertaining.

    Gee whiz...how come she couldn't even get it when the cop was telling her "Ma'am, you're parked on railroad tracks, now please move your car out of the way before the next train comes through and sends it on a one-way trip to the scrapper?" Never mind apparently both

    1. not seeing or hearing the train coming (the headlight and ditch lights half-blinding her should have been a dead-obvious clue, never mind the train horn, considering she was outside her car for at least part of the time it was blowing)
    2. and not making the mental association that 'flashers, gates, bell = train'.

    That's not quite as good as the one time I saw a police truck parked on the industrial lead that serves our local newspaper, though. I wish I had taken a photo of that...
    @FrostCat said:

    To be minimally fair to her, the geometry of the intersection was a bit odd, so she probably thought she was off the tracks. It was basically a T that had a track right past the intersection (I mean tens of feet--I've been past there hundreds of times) and the road turned 90 degrees a few feet past the railroad track: pretty poor layout.

    Coordinates, please? (Or a DOT ID, I can work with one of those too.) Because that does sound like a case of horrific geometrics, no matter how you slice it.


  • Discourse touched me in a no-no place

    Well now, I'm not sure if I remembered it wrong, or if they've moved things around. Here's the coordinates:
    J Verne Smith Pkwy
    Greer, SC 29651
    34.931112, -82.190660

    If you look, the road west of SC-80 is S-42-641, which is Dobson Shed Road on the other side. I would've sworn the tracks were just inside the hook on S-42-641, but it's been 7-8 years since i lived there.

    Oh, wait, I found the video! She was parked in a way that she was facing away from the oncoming train, totally absorbed in her phone call. I guess I was wrong about the geometry.



  • @FrostCat said:

    Oh, wait, I found the video! She was parked in a way that she was facing away from the oncoming train, totally absorbed in her phone call. I guess I was wrong about the geometry.

    It's even worse than it looks. She had turned off the crossing and onto the railroad roadbed...idiot

    At least the cop got her out in time. She didn't run back towards her car as I initially thought, either.


  • Discourse touched me in a no-no place

    Do they only put brakes on the engine car or something? Modern train braking systems are a hell of a lot better than they used to be, so they should have been able to spill a lot of that speed before the impact given that nowhere in the US outside the NEC actually runs real high-speed configurations. (Next you'll be telling me that they also don't put power to all the wheels; that those carriages are just dead weight. But that would be ridiculous…)


  • Discourse touched me in a no-no place

    @dkf said:

    Do they only put brakes on the engine car or something?

    Look at that map again. Based on the video, the woman was parked on the south side of the minor road. That meant the train had just come off of the NE-bound track parallelling US-29. (It had to be that way, not SW, because the train was headed to DC, but it doesn't matter because either way) it had just come around a curve and couldn't have had more than 1000 feet of warning, assuming perfect visibility, and it might have been half that. And it was about midnight.



  • @dkf said:

    Do they only put brakes on the engine car or something? Modern train braking systems are a hell of a lot better than they used to be, so they should have been able to spill a lot of that speed before the impact given that nowhere in the US outside the NEC actually runs real high-speed configurations. (Next you'll be telling me that they also don't put power to all the wheels; that those carriages are just dead weight. But that would be ridiculous…)

    They still aren't as good as you think. A well-equipped passenger train will need a quarter of a mile or so to brake to a stop at as close to a max rate as it can without risking throwing itself off the tracks in the process (slam on a train's brakes too hard, and you can run the slack in to the point of derailing yourself). Freights take much longer (typically quoted as a mile or so) due to the extra mass/momentum and length. (Freight trains nowadays are long enough that the speed of sound introduces significant delay into the braking process. ECP brakes will fix that, once we can get over the hump of implementing them usefully without breaking backwards compat).

    And no, unless you're talking the occasional commuter MU (or rapid transit trains), passenger service in the US of A is still loco-hauled. (European EMUs and DEMUs can't run on the US rail network as they aren't built heavily enough to be run into 10,000ton unit coal trains at speed, head on.)

    @FrostCat said:

    Look at that map again. Based on the video, the woman was parked on the south side of the minor road. That meant the train had just come off of the NE-bound track parallelling US-29. (It had to be that way, not SW, because the train was headed to DC, but it doesn't matter because either way) it had just come around a curve and couldn't have had more than 1000 feet of warning, assuming perfect visibility, and it might have been half that. And it was about midnight.

    Yeah. 1000' is about enough warning at track speed on your typical mainline to slam on the brakes and duck (if you're lucky/quick, you can get off an emergency broadcast on the radio).



  • @tarunik said:

    Freight trains nowadays are long enough that the speed of sound introduces significant delay into the braking process.

    Wut? Maybe I'm engineering stupid ( very possible ). But how does that work??


  • Discourse touched me in a no-no place

    I assume he means this.

    TL;DR: the entire train's brakes are powered by compressed air coming from the engine. It would take a while to reach the back.



  • Read it.

    Seems today's brakes ( supposing I've actually comprehended the article... brandy again...) are released by compressed air. Loss of compression initiates braking. Depending on the extent of distributed power ( or radio telemetry ) systems it can take some time for braking to propagate to the caboose ( do they have cabooses anymore? ) from the engine.

    Not sure where speed of sound factors in however...



  • Not sure where speed of sound factors in however...

    Say you have a long tube, full of compressed air. And you open one end. There will be a pressure differential between the open end and the other end. That differential will equalize "at the speed of sound".

    Put another way, all the brakes won't start braking at the same time. The brakes at the end where pressure is released will start immediately. The brakes 343 meters away will start a second later, etc.



  • If I read the article correctly, the pressure release is a local phenomena to each car ( they each have release valves ) so that should be relatively quick1. For “charging” the system, sure, I can see the propagation taking “mach” time. That does explain why it takes so long for a train to “start” as each car “pressures up” and the brakes release.

    1 Modulo the power/radio braking signal efficiency and mass issues.



  • As far as I can tell, it's not local. The driver's brake valve causes pressure to lower in the brake pipe, and that causes the pads to engage.

    http://www.railway-technical.com/air-block.gif

    Actually, I think we're both right.

    http://www.railway-technical.com/airbra-rel.gif

    It looks like the brake pipe sends a "control signal" that moves at mach speed, and then each brake does its own air pressure thing locally.



  • @Captain said:

    Actually, I think we're both right.

    Agreed.

    http://www.noogenesis.com/pineapple/blind_men_elephant.html


  • It's nice to see some crossover between my startup tabs. Greetings from the nicest imageboard, family friendly http://www.1chan.net/rail/!



  • @Captain said:

    Angle Cocks


  • Discourse touched me in a no-no place

    @tarunik said:

    European EMUs and DEMUs can't run on the US rail network as they aren't built heavily enough to be run into 10,000ton unit coal trains at speed, head on.

    If you're running a passenger train head on into a freight train, You're Doing It Wrong. The relatives of the passengers will agree with that. Consider going to more dual line operation, especially on routes carrying passengers, so that you don't need to have trains going in opposite directions on the same set of rails. (Bonus: you also get more efficient freight operations.) Also consider whether your signalling system is up to the job; the signalman should always know what blocks are occupied by trains and thus what blocks it is safe for a train to enter.

    The more I hear about US rail operations, the more I wonder what you idiots are up to. It's like you collectively only know how to run a freight railway, and then only in a “slap some more mass on it” way.



  • @dkf said:

    The more I hear about US rail operations, the more I wonder what you idiots are up to. It's like you collectively only know how to run a freight railway, and then only in a “slap some more mass on it” way.

    This is true.

    Passenger rail went to shit the instant air travel became cheap enough. (Except commuter heavy rail.) And our loading gauge is like twice the size of most European systems. Only Russia has a larger loading gauge. So we can put pretty fucking huge things on our tracks. Like 737 fuselages.



  • Sometimes we ship them, sometimes we try to use them as ships.



  • +


  • Discourse touched me in a no-no place

    I think the one on top of the hill fancies the one that's not in the water yet. Now I'm shipping while I'm shipping.



  • People still ride trains?


  • Discourse touched me in a no-no place

    Europeans love trains, don't they?

    We still use 'em in the US, but not as much as them.



  • It's all about distance. cities like New York, Chicago, and Boston have pretty good train systems. other cities, like San Diego and Los Angeles, not so much. we're more spread out.



  • The high speed train between San Fran and LA is doomed to failure. And that doesn't even leave a single State.

    Europeans generally have no idea how spread-out the US is. Of course the US is nothing compared to Australia, but.



  • While I agree with you on this part, I'm wondering why you think it is doomed. My own expectation is that NIMBY on the part of the counties it would pass through would make it impossible to get the necessary routes, but there are plenty of other factors that could kill it. What's your take on it?


  • Discourse touched me in a no-no place

    All kinds of reasons, starting with "ballooning costs" and moving right on to the hilarity of greeny BANANAS filing lawsuits. Plus the fact that for various reasons it will never truly actually be high-speed, so it won't save you a lot of time compared to other methods of travel, even when complete. Also, when you get there, now what? You walked off a train without a car into the middle of a city that's not suitable for a person without a car.


  • Discourse touched me in a no-no place

    Oh, and back to the money issues: there's the one about the fact that they're trying to ignore the plain language of the law that says it can't start without the rest of the money being secured[1], which is certainly going to trigger lawsuits.

    [1] I CBA to look up what exactly the details are, so take it as admitted this is an oversimplification.



  • @FrostCat said:

    Also, when you get there, now what? You walked off a train without a car into the middle of a city that's not suitable for a person without a car.

    Does your car go on the plane as hold luggage, or is it carry-on?


  • Discourse touched me in a no-no place

    @tufty said:

    Does your car go on the plane as hold luggage, or is it carry-on?

    Neither. I have the luxury of not needing to fly.

    And having said that, the idea of renting a car for the other end of an intrastate train ride? Seems like a lot of work, not to mention a relatively large amount of money for a day trip. And if you're going to be there longer, why not just drive?



  • That would be a reasonable point in most states, but we're talking about a 400 mile distance in this case.

    OTOH, we're talking about high-speed rail: unlike air travel, where weight is at a premium, there's no good reason why it couldn't carry automobiles. True, it would be damn expensive, and probably cheaper to rent a car at the other end for most people, but it would be a possibility.

    On the gripping hand, this really only counts for going from SF to LA. If you are going to San Francisco and don't plan on leaving the city itself, a car is more of a liability. You would have better luck driving a car into Manhattan than San Francisco, and even if could get around in the traffic, there are the $5/hour+ parking fees to contend with. Better to park outside the city and take BART or MUNI in. As for the rest of the Bay Area, well, do you really want to be driving your own car in Oakland or San Jose (or even, Eris forfend, Richmond), or on the bumper-car game that is I-280 for that matter? Drivers in Boston and Atlanta are worse, true, but Bay Area drivers are much pretty nuts.


  • Discourse touched me in a no-no place

    @ScholRLEA said:

    True, it would be damn expensive, and probably cheaper to rent a car at the other end for most people, but it would be a possibility.

    Have you looked into that? Years ago I had to drive from Miami to Maine; I looked into riding Amtrak for the first part of that because they have a line that lets you take a car for several hundred miles.

    You aren't kidding, damn expensive. IIRC it was about $250 for me and (I don't remember exactly but) something like $400-600 for the car. And that was for a fraction of a 1500-mile trip. In the end, it was cheaper but somewhat longer to drive.

    And of course car rental eliminates anyone without a credit card or who's under 26.


  • Discourse touched me in a no-no place

    @ScholRLEA said:

    Drivers in Boston [...] are worse

    I love hearing people say that. Boston drivers are mostly pretty rational; they're just not into cutting other drivers slack.

    You wanna see bad drivers, spend time in southern Florida. When I lived in Fort Lauderdale, you would routinely see 5-10 cars run every single red light because they were afraid the person behind them would hit them due to not slowing down because they expected to run the red light themselves. And that kind of attitude--fear, and ignoring the laws--informed every other driving choice. I've lived all over from Texas to Boston and nobody drives like Florida drivers.



  • @FrostCat said:

    And of course car rental eliminates anyone without a credit card or who's under 26.

    Is this an American thing? I've been hiring cars and vans since I was 21.
    Sure, under 25 you get a smaller choice of company or car and occasionally pay more, but it's possible.


  • Discourse touched me in a no-no place

    @loopback0 said:

    Is this an American thing? I've been hiring cars and vans since I was 21.Sure, under 25 you get a smaller choice of company or car and occasionally pay more, but it's possible.

    Yeah. Generally speaking car rental places won't rent to you if you're under 25. It used to be that they wouldn't rent to you if you had a debit Visa/MC as opposed to a credit card, too. Admittedly it's been a long time since I was 25 so that might have changed.


  • sockdevs

    Last summer a buddy and I drove around the States. 7250 miles over 18 days... in a Jeep. We spent a lot on gas in those 18 days, never did total it up but we were filling up twice a day most days if not three times a day, and invariably putting in best part of $50 a time.


  • Discourse touched me in a no-no place

    People from Europe don't realize how dang big this country is until they do that.

    The other thing is--I bet you never went anywhere where you needed another language than English. Euros like to knock us for only being monolingual, but as I said to a Belgian a decade ago: you start in Portugal and drive 1000 miles, you really only have one direction you can go, but you'll need to know 8-9 languages to get by (discounting the fact that so many Europeans speak English, of course...) but I could drive 1000 miles or more in any direction but East (I was in DC at that time) and know that I still only need English to get by.


  • Discourse touched me in a no-no place

    @FrostCat said:

    People from Europe don't realize how dang big this country is until they do that.

    And I really mean that. I've driven the length of the East coast a dozen times. It's 1500 miles or more. I've driven from Wisconsin to South Carolina, South Florida to Texas, and so on. These are trips that have you in the driver's seat for 20+ hours (and I mean that; that's not counting time to stop to eat, gas up, etc.)

    This is a frickin' HUGE place. And it's nowhere NEAR full (except maybe in a couple of places.) It's why we don't have a passenger rail system--you'd need 50 times as much rail as Europe does.

    We have a joke here in Texas, about how we'll drive 5 hours to try out a new restaurant.


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