Advantages of Elevated Rail

Here in the Midwest, the most iconic semi-local transit infrastructure is, naturally, the Chicago El, and specifically the Loop.

While the El is not entirely above ground (the Red and Blue lines go underground through downtown), the name and the brand are both about the elevated lines. This contrasts strongly, of course, with a city like London, where the most significant and iconic intracity rail network is literally called the Underground (though, as we'll discuss below, the DLR is often elevated, and there is of course a whole system called the Overground as well).

I also recently visited Montréal, which is building out two different mass transit lines on very different principles: one tunneled belowground and one elevated above it. And one of them is way over budget--the one with the tunnels.

So naturally, I have some thoughts on why elevated rail works well, and why (given those cost advantages we're seeing in places like Montréal) more cities should use it.

To be clear, I'm not saying we shouldn't ever tunnel. There's lots and lots of places it makes sense! I've been snowed on at a Chicago El station and cursed the choice to be aboveground! But given the mounting evidence that elevated lines are quite a bit cheaper, I want to focus on non-cost reasons that elevated rail can be pretty darn good on its own.

1. Look Around You

Most obviously, an elevated train gives a new view of the city: one at least a story up, and often criss-crossing parts of the city that might not be as naturally connected on street level.

This view, from next to the elevated metro station at Amsterdam Sloterdijk, is an angle you can't see without being up top. Perhaps it's not as impressive as others (I could have found a picture, say, of downtown Chicago) but I like the way it shows the sense of the city, as altered from a height. You can see other infrastructure (hello cute little tram!), you get a real sense of the size of the bike parking (which is much less impressive when the bikes block each other), and you can also see the rest of the city peeking out from behind the developments near Sloterdijk itself.

And of course in cool automated systems like the Vancouver SkyTrain (above), the REM, or the DLR in London, that view is out the front of the vehicle, unimpeded. You don't get those trees underground!

2. See and Be Seen

But you don't just see from an elevated line. You are also seen.

I don't really have to ask where the DLR station is at Canary Wharf, do I?

Elevated lines are highly visible and easily identifiable. I don't have to see a little sign to know there's a stop.

Sure, this T sign is iconic! But it's also kinda small, and doesn't tell me which direction the trains go.

This does; thanks outer boroughs of NYC!

Again, this isn't the be all and the end all of transportation needs, but it's nice to be able to see the lines and stations without effort.

3. Flexibility

There are places that are not easy to tunnel in: either they're really hard rock, or conversely too soft and shifting to stay in place, or there's some kind of deposit in the way, or you're in Rome and every dang meter of construction hits another archaeological find.

There aren't many places where factors like that make building elevated rail impossible. The only factor there tends to be local opposition--which is a serious problem, don't get me wrong, but isn't exactly absent from underground digging either. Building the actual elevated line is the easy part, in a way that it often isn't for underground construction, except maybe cut and cover--which likewise produces massive resistance in many cases, and still requires certain conditions for the underground space being used.

If you can build a road, most of the time you could build an elevated line too, since you have the right of way. 

I don't mean to say all roads should become elevated transit, don't get me wrong. I'm just saying that as a mode, elevated rail is more flexible in where it can go and how than an underground line.

To be fair, this cuts the other way with things like mountains.

There's a reason the REM goes under, not over, Mont-Royal. 

But by and large, even if an elevated line weren't cheaper (because I said I wasn't talking about cost!) it is easier to build. And given the transit deficit of so many cities, especially in North America, that's not nothing.

Both subways and elevated rail have their merits, and as long as the transit is getting built I'm for whatever there is political will and economic power to build. But it's well worth considering that elevated rail isn't inherently a case of cheaping out: it has other benefits as well.