I seem to recall that it was deliberately chosen for incompatibility, so that a BART train could never be run on a regular railroad track.

Why? Partly politics. Southern Pacific Railroad was the existing railroad in San Francisco. They had an existing commuter rail operation (which, if I understand correctly, later became Caltrain), and they didn't want the headaches of BART trains on their tracks. They were already losing money on their existing commuter operation. Their money came from hauling freight.

But the other reason was safety. If two trains collide, and they're both passenger trains, they'd better be built to similar collision standards. Otherwise the stronger train will destroy the weaker, and there are people in the weaker train. And if there are freight trains on the same tracks, then the passenger trains have to be built to standards such that a collision with a freight train isn't a massacre. (By the way, this is part of the distinction between "light rail" and regular rail. They should never be on the same tracks.)

> If two trains collide, and they're both passenger trains, they'd better be built to similar collision standards.

Is this _really_ a concern? This sounds crazy to me, how likely are trains to actually collide? Are they not monitored and tracked? Do they not have safety systems?

BART has a safety system that can detect the presence of trains based on the electric potential across the tracks (since the wheels are metal). There was a collision back in the 1970s or 1980s because the repair vehicles had rubber wheels are were therefore not visible to the safety system. A BART train collided with one of the repair vehicles and killed one of the repairmen.

They do have signals and safety systems, but things go wrong anyway. Cast your eyes over the last 10 years worth at https://en.wikipedia.org/wiki/List_of_rail_accidents_(2010%E...

Romania, December 2019: two trains collide almost 50 injured.

And what is more monitored and tracked than airplanes? December 2019: "Wizz Air A320 within seconds of head on collision with an Air Europa Express flight over Spain"

Airplanes are not tracked( as in, they run on tracks) so they have more options as to where they might be. With trains it's far far simpler to position. Being on a collision course should be obvious.

Funny, I'm form Romania too, and CFR is a shining example of mismanagement. I really doubt we can extrapolate a general rule from what is happening with CFR. Precautions and some automated safety systems could surely avoid this.

Trains are tracked, which means they can't get off a collision course. A plane can turn in 2 directions in each of 2 dimensions.

I've never heard of this and don't see how it's possible given that BART requires an electrified third rail to operate at all. Caltrain uses locomotives.

You can have a third rail beside tracks that diesel locomotives use.

That depends on the width of rolling stock.

Plus, I've never seen electrified rail where the right of way is easily accessible by the public and has street-level crossings, and I can't imagine how that could work.

> And if there are freight trains on the same tracks, then the passenger trains have to be built to standards such that a collision with a freight train isn't a massacre. (By the way, this is part of the distinction between "light rail" and regular rail. They should never be on the same tracks.)

Yeah, otherwise every few years we might end up with a collision with the kind of death toll you see in a normal month on the roads.

There is kind of an official explanation for the non-standard gauge:

Western Railroader June 1965 Vol 2806 Issue 305: “Clara (the test car) arrived at Concord from Sacramento in a special Sacramento Northern train. She rode on a WP flat car instead of on the rails since she has a 5′ 6″ gauge, nearly a foot wide thant the 4″ 8.5″ standard gaguge used by most existing transit systems and all the nations railroads. Parsons Brinckerhoff- Tudor Bechtel, the districts consulting engineers, said that exhaustive studies show the wide gauge provides great stability and smoother riding qualities for the rapid transit trains.” [0]

However, the most likely explanation is that during planning, dubious reasons like the one above were given to convince officials that a non-standard gauge would be better. After it was built, the company which build the first rolling stock had a monopoly. So the reason most likely is classic lobbying.

[0] http://www.bayrailalliance.org/question/why-does-bart-use-wi...

"In the matter of reforming things, as distinct from deforming them, there is one plain and simple principle; a principle which will probably be called a paradox. There exists in such a case a certain institution or law; let us say, for the sake of simplicity, a fence or gate erected across a road. The more modern type of reformer goes gaily up to it and says, “I don’t see the use of this; let us clear it away.” To which the more intelligent type of reformer will do well to answer: “If you don’t see the use of it, I certainly won’t let you clear it away. Go away and think. Then, when you can come back and tell me that you do see the use of it, I may allow you to destroy it."

G.K. Chesterton - The Drift from Domesticity

Yes, that's the beginning of the article. Although according to Wikipedia, you gave the name of the chapter, and the article gave the name of the book.

Yes, but you really have to make sure that it is indeed just and accident of history with no other side effects. I can imagine a case where some of the BART tunnels are too short for some trains that run on standard gauge rails, and you don't want someone to accidentally run a standard train over those tracks and get stuck. There is no way to know this without looking. We cannot imagine all contingencies, but we should probably at least look for the ones that we can imagine.

My point was that the conservative approach puts the burden of proof on the new after setting up a bit of a straw man with the reformer. I like the marketplace of ideas instead which favors neither the new nor the old.

Oh it's very much still the marketplace of ideas. It's simply advising buyers in such marketplaces to appreciate track record and acknowledge their own possible ignorance when making "purchases."

As it should be. Doing things as have they always been done means we haven't killed everyone yet. That is quite an achievement when you consider just how hostile to life nature is.

> 5 ft 6 in / 1,676 mm, a broad gauge, is the track gauge used in India, Pakistan, western Bangladesh, Sri Lanka, Argentina, Chile, and on BART (Bay Area Rapid Transit) in the San Francisco Bay Area.

https://en.wikipedia.org/wiki/5_ft_6_in_gauge_railway

So actually it _is_ common - mostly in and around India.

So maybe here is the original vision for the BART: https://youtu.be/fWk36h9-meE

;-)

Youre assuming the context of that decision was purely an engineering process, when in-fact it was a political process.

You seem to think we should value one kind of good decision over the other.

I honestly don’t think the world works that way. Check out the O Ring & Feynman. Our social dynamics are often very terrifying and seemingly draconian, if it wasn't for a general trend of improvement and increased quality of life.

Reminds me of the railway gauges, space shuttle and horses ass story, can't find the original link but here's one on reddit which summarizes it, hope i'm not spreading some urban myth: https://www.reddit.com/r/Jokes/comments/5mh5mv/railroad_trac...

The snopes entry is pretty good. https://www.snopes.com/fact-check/railroad-gauge-chariots/

In Dublin, Ireland we have a light tram system called the Luas.

There is a green line and a red line -- they don't connect but nearly do as they are close. They have different guages.

It's planned that one of the lines will be upgraded to a full metro in the long term however many people think that such a fundamental descision was a simple oversight.