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How we slowed the subway down

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Re: How we slowed the subway down

#71

Post by rocqua »

lifeisstillgood wrote: post #69
rocqua wrote: post #66

Earlier quoted context omitted.

Self-driving convoying essentially boils down to doing this. The problem in your approach is fully locking the brakes rather than slightly decelerating the car. I'd also guess that after 2 years of your system most people would manage to keep their distance. Would probably work great except for merging.

I am however convinced by the "less cars, not self driving cars" argument. Urban redesign, reclaiming back some of the on average 1/3 of city surface area dedicated to cars / roads, more reliable public surface transport (I mean are we seriously asking "can we increase the likelihood of a subway crash in order to increase capacity" instead of asking "why don't we have hundreds or thousands more buses on the roads"? T…

In America, you are presumably correct, though it is somewhat of a false dichotomy. In less car based countries like my home country the Netherlands, there isn't as much room for 'less cars' (though still plenty, just nowhere near as bad as America). Hence self-driving cars here are more important.

Besides the solution in America is likely to be both less cars and self driving cars. So it's not like self driving cars aren't worth developing. They are, however, not an argument that "we don't need to get alternatives to cars".

Re: How we slowed the subway down

#72

Post by digbybk »

atoav wrote: post #49
o10449366 wrote: post #38

Earlier quoted context omitted.

Unfortunately, it's a pretty tired HN comment to posit something as being more simple than it actually is. Even during the pandemic there were widespread complaints about the signal work on the L line that has now transformed it from one of the worst lines to one of the best. There's no such thing as "simple work" on a system that millions of people depend on for consistent uptime.

If you count in the financial constrait that service is working under, sure. But meassuring the speed/position of a rail vehicle on a piece of track reliably is not an unsolvable feat of hardware engineering. It is done elsewhere and it is done elsewhere where similar constraints for uptime exist. Theoretically by that logic we could argue that trains are hard because making the motors for them is non-trivial. It is…

You’re correct, it’s not unsolvable, which is why it is being solved. It’s just a slow process, for the reasons mentioned.

Re: How we slowed the subway down

#73

Post by vlovich123 »

pantalaimon wrote: post #41
hadlock wrote: post #39

Earlier quoted context omitted.

My 1955 Citroen (designed in 1933) has the original speedometer and speed sender cable. It's accurate (GPS tracked) to within 2-3km/h. This is with nearly 70k miles on the clock. This is the same mechanism Citroen used in their 2CV from 1946 until 1992. Most Model A Fords from 1929 have their original speedometer (which works fine, might need greasing every few decades though). With tens of thousands of miles on them…

GPS doesn’t work underground though. But the problem described in the article seems rather unique to NYC and one has to ask how other subway systems manage just fine without artificial slowdowns.

You can simulate the GPS if you wanted to, drop cables down to pipe through the real signal, or simply do very basic positioning with custom radios underground.

OP is correct. We have significantly better techniques.

Re: How we slowed the subway down

#74

Post by phist_mcgee »

Symbiote wrote: post #55
hadlock wrote: post #39

Earlier quoted context omitted.

My 1955 Citroen (designed in 1933) has the original speedometer and speed sender cable. It's accurate (GPS tracked) to within 2-3km/h. This is with nearly 70k miles on the clock. This is the same mechanism Citroen used in their 2CV from 1946 until 1992. Most Model A Fords from 1929 have their original speedometer (which works fine, might need greasing every few decades though). With tens of thousands of miles on them…

For what it's worth, a metro train does around 100,000 miles per year .

And every single one of them invariably is when i'm not onboard.

Re: How we slowed the subway down

#75

Post by gambiting »

Symbiote wrote: post #55
hadlock wrote: post #39

Earlier quoted context omitted.

My 1955 Citroen (designed in 1933) has the original speedometer and speed sender cable. It's accurate (GPS tracked) to within 2-3km/h. This is with nearly 70k miles on the clock. This is the same mechanism Citroen used in their 2CV from 1946 until 1992. Most Model A Fords from 1929 have their original speedometer (which works fine, might need greasing every few decades though). With tens of thousands of miles on them…

For what it's worth, a metro train does around 100,000 miles per year .

So do most normal trains, and they all have speed gauges that work fine, rain snow or dust. Clearly the technology exists.

Re: How we slowed the subway down

#76

Post by LikesPwsh »

interstice wrote: post #60
jimmyswimmy wrote: post #35

Earlier quoted context omitted.

While i agree that it is surprising that MTA continues to use archaic technology, I don't the solution is nearly as simple as you pose it. Hardware engineering is hard, and in-service engineering of complex systems desiring near 100% uptime is challenging. The sensors must not simply survive a dirty, dusty environment, they must work perfectly with no glitches and for long periods between maintenance. And if they do…

Is there a term for using multiple redundancy and statistics to solve issues, for example using 5x 99% reliable sensors rather than a single 99.99% sensor that costs 100x more?

"redundant systems"

Re: How we slowed the subway down

#77

Post by bregma »

pantalaimon wrote: post #45
mildchalupa wrote: post #28

One of the things that I find interesting in terms of long lasting standard or infrastructure development is that small variations in design choices early in a system result in radically different performance down the line. For instance the width or guage of a train track will greatly influence the carrying capacity and the size of objects transportable via rail. Same for the size of lane of road. Infrastructure, and…

The subway is actually a systems that is easier to change than others (unless you talk about the physical dimensions of the train) since it’s an isolated system and lines are usually separate too, so you don’t have to change it all at one.

You're not describing the New York City subway. The L line was separated from pretty much everything else so it got upgraded to CBTC over a few years as budget, time constraints, and politics allowed. The rest of the network is thoroughly interwoven and runs 24x7. It also carries more people daily than all the other systems on the continent combined.

Re: How we slowed the subway down

#78

Post by vladvasiliu »

Symbiote wrote: post #55
hadlock wrote: post #39

Earlier quoted context omitted.

My 1955 Citroen (designed in 1933) has the original speedometer and speed sender cable. It's accurate (GPS tracked) to within 2-3km/h. This is with nearly 70k miles on the clock. This is the same mechanism Citroen used in their 2CV from 1946 until 1992. Most Model A Fords from 1929 have their original speedometer (which works fine, might need greasing every few decades though). With tens of thousands of miles on them…

For what it's worth, a metro train does around 100,000 miles per year .

That's fair. And also, the environment is probably different, as in more dust in the tunnels, etc.

But to stick with French technology, the Paris metro, for all its issues, does have working speed gauges. Some lines still use rolling stock from the 60s and 70s.

Re: How we slowed the subway down

#79

Post by termy »

hadlock wrote: post #39
jimmyswimmy wrote: post #35

Earlier quoted context omitted.

While i agree that it is surprising that MTA continues to use archaic technology, I don't the solution is nearly as simple as you pose it. Hardware engineering is hard, and in-service engineering of complex systems desiring near 100% uptime is challenging. The sensors must not simply survive a dirty, dusty environment, they must work perfectly with no glitches and for long periods between maintenance. And if they do…

My 1955 Citroen (designed in 1933) has the original speedometer and speed sender cable. It's accurate (GPS tracked) to within 2-3km/h. This is with nearly 70k miles on the clock. This is the same mechanism Citroen used in their 2CV from 1946 until 1992. Most Model A Fords from 1929 have their original speedometer (which works fine, might need greasing every few decades though). With tens of thousands of miles on them…

Go fix it then :p

Re: How we slowed the subway down

#80

Post by Gordonjcp »

Symbiote wrote: post #55
hadlock wrote: post #39

Earlier quoted context omitted.

My 1955 Citroen (designed in 1933) has the original speedometer and speed sender cable. It's accurate (GPS tracked) to within 2-3km/h. This is with nearly 70k miles on the clock. This is the same mechanism Citroen used in their 2CV from 1946 until 1992. Most Model A Fords from 1929 have their original speedometer (which works fine, might need greasing every few decades though). With tens of thousands of miles on them…

For what it's worth, a metro train does around 100,000 miles per year .

So, considerably less than the average articulated lorry, or indeed Skoda Octavia?
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