How Many Tracks Do Train Stations Need?
pedestrianobservations.com
pedestrianobservations.com
For example:
* Penn Station Dwells are not limited by passenger movement at doors. It’s not a metro, go and watch trains being loaded.
* Escalators constrain the rate at which people can actually reach the platforms
* These escalators need to switch direction when a train arrives, meaning multiple arrivals and departures are not simultaneously supported.
* The tracks do not support all operators and the station design divides Amtrak from LIRR
* Some tracks do not support full train lengths
* Not all tracks in the station are through tracks
* Trains are terminating at NYP which requires a longer process of ensuring no passengers are still on on board before leaving for the yard.
* It’s not only the north and east river tunnels, there is an entrance from the Empire line for Amtrak and separate paths to the WSSY for LIRR, not to mention train storage within Penn in the ACDE yards.
* Engineers walk the entire length of the train when a trip reverses direction. This takes a long time. The OP mentions through-running solution, but doesn’t point out the problems with it, namely incompatible equipment and giving an entirely different agency access to your multimillion dollar trains.
I could go on and on.
Let people wait on the platform as the train arrives. This is something that basically every train operator but Amtrak does.
> The tracks do not support all operators and the station design divides Amtrak from LIRR
This isn't a problem... trains in most stations are already basically scheduled to an individual platform anyways.
> Trains are terminating at NYP which requires a longer process of ensuring no passengers are still on on board before leaving for the yard.
Through-run trains. Yes, this requires cracking some heads at NJT and LIRR (and MTA before much longer). Is it really worth spending billions of dollars to avoid having to resolve agency turf fights?
Through running NJ Transit onto LIRR is through running AC trains onto a DC network. That is billions. In addition, nobody from NJ wants to go to Long Island and vice versa, and most NJ Trains run-through the station in the same direction already to be stored at Sunnyside. The same is true of LIRR, they go into the west side yard as a straight move. The NJ trains that don’t run to SSY are usually making use of the stub end tracks at Penn where through running isn’t an option.
And that one doesn't need anything but a bridge over a freeway.
I haven't been to penn station in a while but I know the LIRR track numbers aren't available until the train arrives or right before. This dictates which platform to stand on.
Basically you end up standing in a huge open lobby and eventually a big display says to goto track 21, then there's a mad rush of people making their way to track 21 which involves leaving the lobby, going down stairs, and making your way to the track to board the train.
In no small part because the platforms are too narrow — something that getting rid of several tracks would readily fix. (Just fill in the space between two platforms and you have a nice, very wide platform.)
> * Escalators constrain the rate at which people can actually reach the platforms > * These escalators need to switch direction when a train arrives, meaning multiple arrivals and departures are not simultaneously supported.
> * Some tracks do not support full train lengths > * Not all tracks in the station are through tracks
Alon isn't against a station remodel. He is against this one because it is a bad plan. Platforms should be full length for the train that will use them. Platforms should be wide enough for people to wait on them. Penn station needs less platforms that are used better, not more of them that cannot be used very well.
The trains in Tokyo all seem to have nice new signs with upcoming train info next to each of the tracks. That makes it much harder to get on the wrong one. Also, google maps works disturbingly well for Tokyo subways.
It’s the same in Germany. Something like this [0] is at pretty much every train station nowadays, even the small ones.
[0]: https://sbahn.berlin/fileadmin/_processed_/d/b/csm_Ring_anze...
Then covid hit, the city paused train service, I moved out, and I really don't care to commute to work (or school, at the time) again.
Not exactly 'comfortable', but informative. Don't have to use an app, don't need to look at the timetable, don't have to wait in uncertainty. Just go, see, ride, done.
I once boarded a train that had arrived at the correct platform, on time, and to the correct destination. It turned out, though, that I had a ticket for a different train that was late.
People just say ‘the 1030 to Euston’ or whatever. I’m sure they have internal IDs.
That said, we have had dynamic train information displays on all platforms for as long as I can remember (wikipedia says since 1961). When I was young, they used to be mechanical rotary displays [0] (klapperborden, aka "clacking displays", referring to the sound they make when the system was leafing through the pre-printed sheets), but they have been replaced with TV screens or LED matrix displays in most places now.
[0] https://nl.wikipedia.org/wiki/Centraal_bediende_treinaanwijz...
https://www.railforums.co.uk/threads/train-doors-may-close-3...
Personally I think that for the convenience of passengers the doors should not close before the published time, which is traditionally called "departure time" but I don't really care what they call it; the point is that people need to know the time at which they need to be on the train and the easiest way to tell them is to tell them directly without any bizarre offsets.
Is there anything with a departure time where you expect to be able to get on momentarily before departure?
The time given should ideally be when check-in closes - much easier to plan around.
Things I walk up to momentarily before departure: every mode of transportation except planes. For trains and buses, the two times should be almost simultaneous (as anything else is just adding additional linger time)
When the doors open, depending on traffic, they easily spend less than 20 seconds open before closing. I've run for a tube and dove in just in time _so_ many times now.
There's arrival and departure (to the gate, platform, or quay) of the vehicle / vessel itself.
There's ticketing and check-in time, if those are required. Possibly security screening for air travel. And for aircraft, gate arrival time vs. wheels-down / wheels-up, where the latter includes taxi and takeoff queue time. Add to this the reliability or unreliability of actual travel times --- busses and shared-route transit must deal with traffic and delays, aircraft with weather and airport conjestion, ships with dock and pilot availability as well as weather factors, for example.
Schedules are written from several points of view --- the operator (when must vehicles be at specific points or departing from them), passengers, port or terminal operators, etc. Each has different needs. Learning how to interpret the published schedule to your own planning is key to effective use of such systems.
However, you could have the doors close at the beginning of the minute, and the train leave at the end of the minute and have 59 second leeway.
The above is about trains. Buses and trams are more complex and cannot run this way.
Tokyo is a large engineering office for Google (and the first in Asia IIRC). This probably explains it.
The group I work in (Amey Consulting) have built a couple of systems for Network Rail here in the UK, called Quartz and Cosmo. These are analytic systems examine rail delays and delay propagation, especially sub-threshold delays (in the UK delays over a threshold - 2 mins IIRC) have to be reported, but those under 2 mins don't. We started looking at sub-threshold delays a few years ago, and have understood how these small delays build and propagate through the network, affecting multiple services.
We are always recruiting (UK - main sites London and Manchester, some folk in Birmingham too) - so if you have an interest in applying data science to infrastructure have a look here: https://www.amey.co.uk/what-we-do/amey-consulting/careers-wi..., or DM me
Watching a documentary about Crossrail the other day their testing seemed to consist of a driver manually driving a simulator in real-time through signals and recording when buttons don't work etc. I was kind of hoping that was just a misrepresentation.
At least with older trains, you could usually move the train in emergency, even if slowly, but having the software tell you that you can't close the doors or pull away is really bad.
There were also issues with trains missing from the passenger information systems and even worse, a broken down train on the boundary between TfL-controlled and Network Rail-controlled lines and it sounded like no-one knew what to do and it caused 2 hours of messing around.
But beyond this, yes it is a humungous project that keeps humming without major glitches. Supported by a lot of workers on the ground doing tasks like track inspections, cleaning, maintenance day and night.
ref: https://indianrailways.gov.in/railwayboard/uploads/directora...
> The biggest required investments for this are electrification and level boarding. Both have many benefits other than schedule reliability, and are underrated in Europe and even more underrated in the United States.
Neither is underrated in Europe. Both are the norm on new projects, and almost all heavy duty old lines have been upgraded to at least be electrified. However the costs associated are often astronomical ( and might require closing the line for extended periods of time) so for some of the rest it's done piecemeal.
Obviously not saying war or coming later to the party are good things, but it's one of those ironies of humanity.
The idea is that you have a standard electrified OHL system where it is easy and cheap (!!!) to install. Places whee you can't put it easily, such as under bridges, through tunnels etc, you don't. You have some (small-ish) battery capability in the train which recharges from the OHL system, and use that in the areas where the OHL hasn't been installed.
Conversely for historical reasons however in Germany 0.76 m is the highest platform height that doesn't conflict with the loading gauge of "regular" exceptional loads on freight trains (on a very few selected routes intended for the transport of extra large transformators and similar loads actually anything higher than 0.55 m already causes problems).
If you're building a pure high-speed network from scratch without any compatibility constraints (like Japan did with the Shinkansen) you can just choose a platform height of something around 1.1 – 1.25 m and be done with it, but if you're starting with an incrementally upgraded mixed-traffic network as is more common in Europe, you now have a problem…
(Talgo sidesteps this problem because of the unconventional bogie design, where the two wheels aren't linked by a fixed axle and steering is assured by the interaction of neighbouring carriages instead, so even with a lower floor height the floor can simply pass between the wheels without necessitating any steps.)
Another counterexample might be the Giruno (250 km/h), but that in turn needs to compromise on its door location (only a single door per coach, and placed centrally in the middle of the coach).
> long-distance platforms didn't have a height of 960mm already
They don't. 960 mm is only used in various S-Bahn systems and not compatible with the structure gauge of the general railway network.
If a train goes below a highway bridge it's probably too low for the wire, thus the highway bridge has to be replaced (or tracks be lowered) If there happens to be a tunnel the diameter has to be increased.
In many systems you currently have a central hub which is overhead wired. If you then have a unwired branch line installing a third-rail-system there would require vehicles which can use both. Such systems exist, like the underground in Nuremberg, Germany, which operates with a third rail on tracks, but in the maintenance area has overhead power to make work safer. However that increases cost by requiring custom vehicles etc.
> “It is bad enough that Germany is keeping some outer regional rail branches in the exurbs of Berlin and Munich unwired; that New York has not fully electrified is unconscionable.”
There is a strong argument that battery-electric trains will replace the need for overhead electrification on shorter routes and branch lines.
Track electrification can be very expensive, and hard to justify on less-busy lines. But with batteries, a train can charge while running on an electrified trunk line, then continue onto smaller branch lines.
Definitely not!
There is really no scarcity of lithium in the world. If more is needed then it’s easy to just tap new supplies because it’s pretty much everywhere if you go looking.
Battery producers are more constrained by things like nickel and cobalt, but there are alternative, cheaper li-ion chemistries (such as LFP) that do without these.
On long routes the required size of the batteries might become prohibitive. But we’re talking about outer-suburban branch lines here which are usually pretty short, often only a few miles.
Batteries make sense for manoeuvre trains working ports, cargo train depots etc. Small batteries and recharge frequently.
In some cases you do because hybrid (bi-mode) trains exist too! [1] Although as another commenter points out, they are also working on tri-mode diesel/battery trains.
Of course, fully electric trains can just regenerate into the power lines.
(With batteries, an electric train becomes even more reliable because it can continue under its own power in case of a line power failure.)
Batteries are massive (in the weight sense), and frequent acceleration and deceleration as well as safety would be major concerns.
https://www.reddit.com/r/nycrail/comments/l57nw2/map_of_the_...
(LIRR Montauk branch is longer, but I'm less familiar with it.)
It's the duty cycle of the rolling stock.
Running a trainset four times along a 100 mile route, or 40 times along a 10 mile route, you're still travelling 400 miles.
And the stop frequency is likely far higher on the urban route. It's the acceleration that costs, and batteries only save you so much there, even with regenerative braking.
Add in heating/cooling loads, air handling, etc., and there's a lot to consider.
About the only place batteries make sense on rail is where you're moving a heavy load one-way down-grade. There are operating quarry and logging operations which effectively work as battery storage. Laden cars (or trucks) run downhill, whilst regenerative braking charges the batteries. Empties return uphill, slowly, on that charge.
Other than a Soylent Green operation from a mountain resort, few commute rail systems have a suitably matching travel pattern.
We're not talking about 100 miles on battery power here - although there are already battery electric transits that are capable of that and more. For the most part, inter-urban trunk lines in Europe are already electrified.
There are many outer-suburban/regional routes that are, for example, 50 miles along an electrified trunk line then 25 miles on an un-electrified branch line. Currently that means whole route needs to be operated by diesel trains. But a battery train only needs to be capable of doing (eg) 50 miles on battery, then it can recharge when it's running under the wires.
https://www.urban-transport-magazine.com/en/schleswig-holste...
"The longest non-electrified section on the diesel network is 80 km. Under optimal conditions, however, a battery range of 150 km should be possible."
It is a bit of a case of shuffling costs from infrastructure to rolling stocks, trains with batteries would still cost more than a pure overhead line electric, but I guess it comes from a different budget...
I'm not sure of any real reason why you'd use a battery off-track instead of a connection to the electricity grid except as some sort of backup for a power failure?
[1] Bi-mode diesel / electrics also exist of course, which solve the problem in a slightly different way (insert NOX / CO2 v Lithium mining debate here).
For the 515, costs were a big factor. The lead based batteries had to be rented from the manufacturer.
But even if you take current technology into account: A train isn't a Tesla. It needs much more energy to accelerate. Currently, an engine and a diesel tank are much cheaper to buy and especially maintain. They will give you decades of use. How long are your batteries going to last?
Also keep in mind that batteries add tremendous weight, reducing reach again. More weight is especially painful in hilly areas. All of this needs to be factored in.
Bottom line: It's feasible and has been done. Operating costs, however, are a big factor, especially compared to what other technologies get you.
edit: There's a battery version of the Stadler FLIRT [2]. It went 224 km (at about 80 km/h) on one battery charge recently [3]. They will be in operation for DB from the end of 2022 on.
[1] https://en.wikipedia.org/wiki/DB_Class_ETA_150
They would still want enough batteries to accelerate from a dead stop to prevent a 5 minute delay from becoming a 5 hour delay. Energizing the acceleration points would be more about reducing wear on the batteries and prolonging their life.
I don't see why not. There are actually urban routes in London (London Overground) that do this multiple times on every journey! Switching between overhead AC electrification used in North London and the older third-rail DC electrification used in South London.
> "Having lines with spotty overhead is very error prone and reliability is a big factor in rail. "
But that's where batteries come in. Being able to keep moving under your own power if there's a problem with the overhead wires adds a lot of robustness/redundancy.
The cost of raising the panto slightly too early even once is tremendous. You would have to close the track for maintenance. So you need a safety margin of a few seconds. That's several 100 meters. Frequent changeovers would necessitate the system to be fully automated in order to factor out human error.
The changeover on London Overground is usually done while standing at a station (by the driver). According to [1] it's possible to switch while moving. The speed limit is given as 25mph, however.
[1] https://www.railforums.co.uk/threads/changing-from-dc-to-ac-...
Nerd that I am, I walked up to the driver, knocking on the glass and asked: "Moin, do you know your pantgraph is up?" Turned out he didn't, and there wasn't any indication. He got it down by repeatedly switching up/down, and finally it stayed down. Two minutes late!1!! ;-)
Yes, diesel is cheaper to buy than battery trains. But pretty much everyone, including the main article here, agrees that maintenance costs are much lower with electric trains compared to diesel. I'd expect that (at least once the technology matures) this will also be true of battery electrics.
The point is, if you start with the assumption that diesel is unacceptable and routes must be electrified - for reasons like climate change, toxic air pollution, route reliability, passenger comfort, etc, then there are many routes where battery electrics are going to greatly reduce costs compared to installing overhead wires on every section of track.
> "There's a battery version of the Stadler FLIRT [2]. It went 224 km (at about 80 km/h) on one battery charge recently [3]. They will be in operation for DB from the end of 2022 on."
Yes, I expect we'll see a lot more battery electric units introduced in Europe in the coming years. There are so many routes where they make perfect sense.
Indeed, and neither are electric cars. But battery chemistry, electric motors and inverters, and controller software and hardware have all come a long way in that time. The technology is far more viable and efficient today than it was back then!
https://eng.belta.by/economics/view/belarusian-electric-bus-...
"The bus is fitted with a system of super capacitors, which get fully charged within 5-10 minutes while the bus is at an end stop. The bus can travel along the entire distance of the line for up to 15 times per day. On the first day it managed to travel for over 40km on one charge."
There has been some work, a few years back, using super-capacitors (alongside storage batteries) in high-performance electric cars to increase peak power output. But really, battery technology has improved so much that it's made that sort of thing unnecessary. Even your standard Tesla is pulling 8-10C if you really put your foot down.
How long does your battery keep usable if you do that at every single stop? (so every 2 minutes, let's say 300 times a day ballpark)
But for the ones who are doing it repeatedly (at the track), the answer is: very effective battery cooling! Tesla's software in their performance models actually offers a special "track mode" which, amongst other things, applies max cooling.
When Network Rail in the UK looked at electrifying the Great Western Mainline, the majority of the cost is actually in a very small % of track length which is where the line goes through Victorian tunnels and under old bridges.
If your battery only needs to be sized to maintain speed for sections a few miles long at the most, you can get away with much smaller batteries.
I know they are running trials of what are effectively "tri-mode" trains already which are diesel/battery/OHL.
The main problem here is one of politics and human attention span.
It’s easier to drum up a bunch of support towards a construction project. It’s visible, some politicians get credit for it, and you can have a campaign that builds excitement to a crescendo before people move on to something else.
Good operations are invisible because everything operates as the margins and gets small wins. No one gets credit. If they slip just a little then no one notices, so you can borrow a little from operations to find something more visible, and it’s a boil the frog situation. And, finally, people just don’t have the attention span for caring about long-term operations.
I don’t know the solution and I’m not saying the above is good, but any solutions that don’t attempt to address the human and political aspects of public works are going to have trouble.
That was THE reason imo that Andy Byford was so promising as head of NYCTA - he seemed to be someone who would focus on the pragmatic human aspects. Sadly Cuomo made sure Byford had no chance of success.
Japan Chuou line mentioned in the article is still on the old ATS-P system and it runs 28 train per hour. Even older ATS-S system in Osaka runs 16 train per hour on the inner track of the Tokaido line.
The NY Subway made a big fuss of CBTC and that it would allow them to run more train more reliably than their current old ATS system, which I find funny looking at various line in Japan.
In fact, CBTC in Japan is mostly planned for rural line with infrequent service so the amount of infrastructure (track circuit, etc) are reduced
The current signals being replaced by CBTC date from the 1930s, and are mechanically operated. They are literally historical relics. https://www.youtube.com/watch?v=Mjx3S3UjmnA
London runs 36 TPH on the Victoria Line: https://www.londonreconnections.com/2017/ninety-second-railw...
I just checked Line 14 schedule and the most I can find is 34 train per hour, which is approx 105 second headway.
I am not saying that CBTC isn't capable of running higher interval than regular ATS and wayside signal (which is actually a very old technology), but in most case it doesn't matter. Even without moving block of CBTC, a very short static block (say, 100m) and in-cap signally should theoretically have the came capacity as CBTC.
Meanwhile in Germany: a quarter [1] of the network's signal controller stations still runs on levers, wires and semaphore signals - some of these are from the 19th century and I wish I were joking. [2]
[1] https://www.zeit.de/2019/45/deutsches-schienennetz-signalwer...
In Germany, most freight trains run at night because at daytime many tracks are at capacity with passenger trains.
[1] https://www.sfgate.com/opinion/article/Amtrak-has-priority-o...
[2] https://specialty-freight.com/2021/06/us-requires-railroads-...
That doesn't generally apply to the Northeast Corridor though which I assume was being referenced by the mention of the MTA. That said, while it's certainly imperfect, Amtrak is actually pretty reasonable for the most part on that route. Certainly the epic delays that are fairly common on Amtrak long distance trains elsewhere are rare on that corridor outside of major infrastructure problems, such as power failures.
For light-rail transit, shared routes (LRV + automobiles) and traffic signals mean that arrivals are not predictable. Where shared-roadway and dedicated-route segments exist (say, with San Francisco's Muni Metro), hold times must be built in for the dedicated-route travel segments. Train arrivals are highly unpredictable. A level below Muni, on Bart, rush-hour headways through the San Francisco subway are 4 minutes. That's close to the theoretical maximum Alon gives of two minutes.
For conventional heavy rail, boarding / debarking delays, equipment failures, medical emergencies, police activity, level-grade collisions, and other factors, may all lead to service delays.
Signalling matters mostly in that it both doesn't introduce new delays into the system, and that it can compensate for delays originating elsewhere.
Reliability overall, as discussed in the article, is largely based around signalling to manage flows.
That should probably be doable on some american light rail systems, with signal priority and avoiding street running on roads with a lot of traffic congestion.
BART operates up to 80 mph (128 kph), though I'm not sure it hits those speeds within San Francisco.
> though I'm not sure it hits those speeds within San Francisco.
due to the shorter station spacing I'd assume that, too.
As for the stations, the limiting factor in turn consists of the sum of dwell time (wheel stop to wheel start) and platform reoccupation time (governed by the signalling system).
Arguably fixing that by building a fly-under (a tunnel under the existing tracks) fixed a huge source of problems for that part of the UK rail network, probably more so than the signalling.
The article alludes to the need for through tracks although it is perhaps not immediately obvious that this can also be used for main "terminal" stations. In Germany, very few trains terminate in the Hauptbahnhofs (main stations) but instead will then move out, often to another large station or depot outside of the city centre. This allows high traffic into the main stations without blocking them up while cleaning/turning round.
Another issue about level loading is made but it sounds like this is mainly related to the difference between a "road" at ground level needing steps vs a platform at carriage level. However, even in the UK where everywhere uses platforms, there are still issues with level due to the variation in track height related to ballast working so even "mostly level" can be a problem, particularly for wheelchairs and even done efficiently, loading these can easily take a minute or more.
Thirdly, at least in the UK, it isn't just the build up of subtle delays that can be an issue but small problems creating large delays. The other week, trains were delayed and cancelled for hours (for some reason) because a trespasser was seen on the main line and needed to be found by the police. One relatively small and common occurance affected 1000s of travellers. A single signal problem, a broken rail, failed point etc. This means that you could in theory run e.g. Kings Cross Station with fewer platforms but as soon as there is a problem, people don't want to sit on a train for 2 hours somewhere on the line. Having more platforms gives you that flexibility.
If the trainsets are all identical and the platforms are straight, you can get a very, very narrow gap (easily navigated by a wheelchair alone).
I think about this a lot every time I see the glacial pace of the ongoing electrification work for Caltrain on the SF peninsula — "studied" since 1992, groundbreaking in 2017, and hopefully in service by 2025 if there are no additional delays: https://en.wikipedia.org/wiki/Electrification_of_Caltrain
Electric motive power was novel in 1895 when the B&O electrified part of the Baltimore Belt Line, but we should be good at it by now! For comparison, the PRR was able to electrify their line from New York City to Washington D.C (225 track-miles, 1928–1935) in roughly the same amount of time it will take Caltrain to build out their 77 track-miles, at which time 90 years will have passed since GG1s were zooming up and down the NEC at 100mph:
https://thebhc.org/sites/default/files/beh/BEHprint/v009/p01...
https://en.wikipedia.org/wiki/Amtrak%27s_25_Hz_traction_powe...
https://en.wikipedia.org/wiki/Pennsylvania_Railroad_class_GG...
In the UK, they recently electrified a lot of the Great Western mainline and decided to go with a cheaper/quieter type of installation method - auger drills iirc - for the pillars (why not), but at certain points, they started finding large granite boulders from the original railway construction which wouldn't be drilled, which meant new plans, new equipment, new training and loads of cap-ex when they were still years away from service. They also found tonnes of electrical system conflicts which meant whole signalling systems being replaced even before they had life-expired.
I love trains and I love modernisation but most of us underestimate the enormous amount of work involved in an upgrade like this.
It's time we got rid of this.
The train in front of you won't suddenly turn into a brick wall. The quickest it will ever slow down is with its emergency brakes.
And if it applies it's emergency brakes, then your train should also apply your emergency brakes.
So the minimum headway is the reaction time (milliseconds if automatic) plus the worst-case difference in performance between the brakes.
Using that, you can get headways down to a few seconds.
What about derailments? Can a derailment lead to a higher deceleration than the emergency brakes are able to produce? (I don’t know the answer, genuinely curious.)
> So the minimum headway is the reaction time (milliseconds if automatic)
How do the following train detects that the leader train is emergency breaking? Is it based on trackside sensors, or some train-to-train communication?
Yes. But a derailment of one carriage of a 5 carriage train will already likely cause the derailment of the other carriages, and in my proposal the carriages of the train behind. Derailments at speed are already typically deadly.
> How do the following train detects that the leader train is emergency breaking?
I would use train 2 train communication to say "I am not emergency braking" every 1 millisecond. If more than a few of these messages aren't received, then you have to assume the train in front is emergency braking, and act accordingly.
A design like that is important because infrastructure failures are frequently coincident - eg. power loss causes signalling and comms failure due to an untested UPS.
A system checks each plan against the plans of all other trains, and approves them if they are non-colliding. The 'alternate' plans can overlap only if to do so indicates independant failures must have occurred - for example the brakes of train 1 fail at the same time as the traction motor of train 2 gets stuck on max, and comms fail.
Track infrastructure such as signals and points would also submit plans - so that for example a set of points can prevent any trains passing over while it isn't in a safe locked state.
All trains must then follow one of the plans they have approved. If comms fail and they can't get a new plan approved, they must still follow an approved plan - which means they are guaranteed not to collide with any other train.
All plans would be signed with timestamps (to prevent someone maliciously changing them to cause an accident), and would normally be delivered by dedicated rail infrastructure, but could be delivered by 3g/4g/wifi in an emergency. Manual plans could also be entered and distributed, for example via USB stick, for maintenance - such plans would say "I have access to this huge segment of track, and nobody else may enter".
Plan A is used if all systems remain operational. It says that the train will continue to move at 60 +- 5 mph for the next 10 seconds, then slow gradually to 45 mph. The plan could consist of a section of "reserved" track for each second in the future, and the train is sticking to the plan if it remains within the reservation.
Plan B is used if service brake failure happens. It says the train will apply its emergency brake and slow to zero at a given rate.
Plan C is used if both the service brake and the emergency brake fail. It says the train will continue at 60 mph, and may speed up or slow down a little, before finally guaranteeing to stop within 30 miles.
All the plans would be written automatically by software, and each would be 'conservative' - ie. if there are any uncertainties, the plan must include them. Less advanced trains would have wider bigger plans, and must therefore keep wider separation distances.
Plan C is obviously very unlikely - and is therefore allowed to overlap with similar plans B and C of other trains - the reasoning being it is very unlikely for the service and emergency brakes of this train to fail, at the same exact time as the emergency and service brakes of another train.
I like that. How would that work when there is no lead train? In other words how would a train know that it is not hearing from the train before it because there is no train, vs not hearing because the lead train is damaged/emergency braking.
It doesn't solve the problem of 'there is a tree on the tracks' or 'someone put a homemade train on the tracks' - you need a different solution to that.
Your proposal would have the derailment bring down that train, and have another train potentially slam into it.
Derailments stop a train much faster than the brakes ever could.
https://www.seattletimes.com/seattle-news/train-derails-from...
But when if the first train is experiencing something it shouldn't, like a big accident/derailment, the landscape could be a way better brake than the train's own brakes. When does the second train start its emergency braking?
A passenger train in emergency will stop much much faster than a freight train in emergency, orders of magnitude faster.
I thought train emergency brakes were capable of fully locking the wheels (to the point where they get significantly damaged/deformed after an emergency stop), so why would the braking pad heat dispersion matter?
They don't. That'd cause drift and derailment.
There is a bunch of pictures here[0], and you can spot in some of them where it says "Spor 0". But I assume "track 0" isn't _that_ uncommon after all.
Which leads me to wonder whether a "track -1" exists anywhere.
However, I was in Kings Cross yesterday and was amused when I saw a sign for platforms 0 to 8.
https://indebuurt.nl/nijmegen/genieten-van/mysteries/nijmeeg...
One such (obvious) exception is OK with me. Its annoying when every train station has random track numbers though.
Tracks are numbered logically or at least start out that way, but in some stations, many tracks don’t border a passenger platform (which freight trains don’t need)
If there’s a shunting yard nearby, there can be many such tracks. Looking at http://www.sporenplan.nl/html_de/sporenplan/ns/ns_65/nm.html, that may be the case for Nijmegen.
I don’t know what rules they use for renumbering tracks, but they must weigh the cost of redocumenting things and retraining personnel (likely the trickier part. Some of them may have known the track numbers for decades, so reassigning number to make them easier to learn can be risky. From a safety viewpoint, moving from 1,2,3… to A,B,C… may be a better option) against the training of future employees.
In France sometimes tracks aren't numbered but lettered. Sometimes they're both - e.g. the same train station can have tracks A, B, 1, 2, 3, 4 ( e.g. Avignon TGV, where 1 and 4 are for stopping high speed trains, 2,3 are for passing through high speed trains, and A(maybe also B, don't remember) is a separate track terminating at that station for the commuter rail link to Avignon's main railway station). Sometimes there are weird likes like only two tracks, one is 1bis, the other A. Or 1 and 1bis. Usually it's related to the historical evolution of the train station ( e.g. in the 1/1bis case it was a single track station which was expanded).
[1] https://www.aargauerzeitung.ch/panorama/vermischtes/in-aarau...
edit: Not meaning to say they don't have giant stations, but the passenger parts don't look like this.