If you want to move more buses, you need more bus terminals. If you want to move more planes, you need more airports. If you need to move more trains, you need more train stations.
The point about scaling air traffic and scaling trains is that you need far less infrastructure to get a plane from place to place. You don't actually even need a huge, expensive airport to do so, since there are much smaller ones and even just tiny airstrips. And unlike trains, once they leave, they have pretty much unlimited room. How many tracks would a train station need in order to accomodate the same number of passengers leaving from Heathrow?
Again, thu2111's statement was:
> "Adding capacity to the sky is easy because it's empty. It's essentially just about scaling air traffic control systems."
ATC systems are not the only relevant part of infrastructure - airports are also important.
You write "you need far less infrastructure". Sure. But airports are also needed for scaling, even if small/tiny airstrips are included, and my point was that airports were omitted from the infrastructure cost.
You write "since there are much smaller ones ... tiny airstrips". That doesn't solve London's capacity problem, which is why a capacity question must include the cost of airports.
You ask "How many tracks would a train station need in order to accomodate the same number of passengers leaving from Heathrow?"
Heathrow has about 80 million passengers per year says https://en.wikipedia.org/wiki/Heathrow_Airport .
London Waterloo has about 94 million passengers per year says https://dataportal.orr.gov.uk/media/1668/estimates-of-statio... , with 24 platforms says https://en.wikipedia.org/wiki/London_Waterloo_station . Looking at the aerial photo confirms there are 24 platforms, and it appears from Google Maps' satellite view that they are served by 7 rail lines, splitting into 24 platforms.
So, 7 tracks are enough to accommodate the same number of passengers leaving from Heathrow.
However, that answer doesn't make a whit of difference to my point, which is that if ATC is important cost facto to bring up when discussion air transit capacity, then airports are also an important cost factor.
All of the biggest airports have had extensive and expensive work done to increase capacity. SFO is about 90% of capacity, if I read https://www.faa.gov/airports/planning_capacity/profiles/medi... right. And it's worse if the weather is bad.
That's why I argue that you cannot ignore airport capacity in your estimates.
We can look at the inter-war period to see how capacity calculations had to consider more than just the sky. Pan-Am famously ran flying boats in their transoceanic lines. "Their advantage lay in using water instead of expensive land-based runways, making them the basis for international airlines in the interwar period." (Quoting https://en.wikipedia.org/wiki/Flying_boat ).
Indeed, floatplanes are still important in bush flying for the same reason.
I don't know what "pretty journal" means. None of the dictionary definitions seem to make sense. I know the rail lines serving my city are not anywhere near capacity. The train between Santa Fe (my former home city) and ABQ is also nowhere near capacity (see https://en.wikipedia.org/wiki/New_Mexico_Rail_Runner_Express ). A couple of years ago I took the train from San Diego to ABQ. It was also not at capacity.
The problem with rail is the capacity issues affect the entire line. If one station has busy platforms and the rest are all quiet, you can't put additional trains on that line (unless it's a terminal station and there's a turning circle before that station and you are willing to run trains that don't go there). Also if one line shares fast and slow trains, that kills capacity.
One airport can share fast and slow planes, and capacity problems at one airport don't affect other airports.
I guess I'm writing mostly from the British perspective. My comment about fuel taxes paying for the roads is (or was) true for the UK.
Since privatisation at the start of the 1990s decades of decline in ridership turned around and now more people use the railways than ever. In the UK there are lines everywhere that are not only at capacity but drastically over-capacity, e.g. there's a train departing from Euston on a Friday night that carries more than 2x the number of people it was designed for. Despite that Crossrail - one of the biggest civil engineering projects in Europe - isn't even open yet, the country just committed to an even more eyewateringly expensive new rail line that won't be open for over a decade. Primarily justified on capacity grounds.
Heathrow expansion is also very expensive of course. But there's really only one airport in the entire country that has such severe capacity issues, and the expansion is difficult primarily because it's surrounded on all sides by urban development like motorways and villages that have to be demolished and relocated. In the case of the motorway, it's also carrying such large capacity that it can't actually be closed for extended periods, so it has to be moved whilst "live".
I think the USA has a different set of issues because the railways are used mostly for cargo rather than passengers. The large distances involved means air travel is the only feasible mode of transport for many routes, and Americans take internal flights all the time whereas for most Brits I know, internal travel is almost always car or train. Business people take internal flights, and even then only quite rarely. I've traveled Acela and indeed it also wasn't heavily used.
Regarding "kills capacity", aren't passing loops meant to help that exact scenario? https://en.wikipedia.org/wiki/Passing_loop has many details. At the very least, it's not as dire as you describe.
I know little about the UK rail system -- or any country's rail system, for that matter. I do know your rail enthusiasts despise the Beeching Cuts, and that just saying that term is a hot button for some.
As for Beeching, it's not quite that simple. The roughly 25-35% of the country that's pretty left wing hate the Beeching cuts for the same reasons they hate all government cuts.
Despite my negative view on trains above, I'm actually a train enthusiast. I love taking the train. I love reading about how they work. There was a story on HN some days ago where a rail engineer talked in detail about how the high-speed rail record was set, I absolutely loved reading about it. My girlfriend had to tear me away from the screen. And I've often wondered about how to really scale up the railways in a big way.
In a way, railways are kind of the ultimate nerd dream. An ideal railway is a huge, smoothly operating and very safe high performance machine, entirely coordinated by engineers and planners. I think perhaps that's why it's such a political hot-button issue: a nationalised railway represents a very tangible instance of massive state planning and control. Decentralising it is difficult for various logistical and technical reasons, not only the politics of it.
Despite that the Beeching cuts have never been rolled back, even under the 3 terms of Labour government. Many of those lines made no sense, especially in the context of continually declining ridership and the ever rising traffic on the roads. It'd have been a very irrational government that continued ploughing money into rail instead of building motorways given the expressed preferences of the population at the time.
For unknown reasons that are still debated today (but which align perfectly with privatisation), the decades-long decline in train usage reversed and so now new lines are needed again. But they're different routes to the ones closed by Beeching. Those were mostly small rural lines.
One point of "unease" (to quote the Wikipedia entry) is that Marples was pro-road; https://en.wikipedia.org/wiki/Beeching_cuts#cite_note-50
> A more critical interpretation is that after Macmillan named Marples as Minister of Transport, Britain’s transport policy swerved to the right, and became motivated by the kind of conflict of interest that Thompson notes can be loosely regarded as a form of corruption (9). Actually, in this case it may well have been a rather tight form of corruption. At the time that he was named minister, Marples owned 64,000 of the 80,000 shares of Marples Ridgeway, a civil engineering firm that specialised in building roads"
I as an ill-informed outsider cannot disambiguate how much of the shift to roads was from "expressed preferences" and how much was from "a form of corruption".
You wrote "nationalised railway represents a very tangible instance of massive state planning and control".
But .. so is a national road system. Your country spends billions on roads, which is pretty massive.
In the 1970s, protests against the increasing number of children deaths caused by cars resulted in the more pro-cycling infrastructure they have now, rather than prioritizing cars first, second, and third like they did in my country (the US) and, I believe, the UK.
https://www.theguardian.com/cities/2015/may/05/amsterdam-bic... for background.
I can't help but also note that post-war UK manufactured cars, while the Netherlands did not.
While trains are touted as very efficient modes of transportation, and generally beloved by nerds, I'm skeptical, largely because train tracks are so under-utilized.
Train tracks take up as much space as many multi-lane highways. On highways, dozens of cars go by every minute. But a train car only passes through at best a few times an hour. I suspect that if you took one mile of train track and one mile of a highway with the same overall footprint, far more people/goods will move through the highway-mile every hour than the train-mile.
Don't have data to back this up, just a hunch. But if it's true, then even though trains are far more energy efficient than cars, they're likely far less real-estate efficient.
(Also, I do suspect that this is not always true. A heavily trafficked tunnel in/out of Manhattan's Penn Station is probably more efficient real-estate wise than an equivalent tunnel. But that's a very extreme case with super high densities).
But I am confused about your comment. There are two distinct statements. X = "Adding capacity to the sky is easy because it's empty. It's essentially just about scaling air traffic control systems." and Y = "Rails need constant work to keep them in good condition".
I don't believe X is correct, and I gave a counter-example about adding capacity to London.
But that doesn't mean I think Y must necessarily also be invalid. While it seems you interpret my comment to mean that Y is correct? And I don't understand how one can draw that inference. So I don't understand the point of your comment.