Saturday, August 20, 2011

Some thoughts on high-speed rail routing

View European high-speed lines in a larger map

Several months ago, I spent some time trying to map high-speed rail lines in Europe, and was struck by how they were laid out.

The French LGV network, which carries TGVs and other trains, hardly ever goes through cities or towns. The lines usually thread the needle between communities, and rely on connecting lines in order to get trains on and off the faster network. Some high-speed lines aren't like that, though—the ICE network in Germany relies much more heavily on upgrades to existing rail corridors which did slice through towns. That sort of design also seems to be more common on newer parts of the LGV network in France. (Perhaps due to cost pressures?)

There are very few intermediate stations along the LGV network itself. Far from being "transit oriented", the few stations that exist are frequently on the edges of cities or out in the middle of nowhere, miles away from anything (much like airports). There are a few places where that isn't the case, but usually only in fairly large communities.

In many ways, this strikes me as similar to how the Interstate Highway System is built in much of the U.S. It also tells me that truly great high-speed rail can't exist all by itself—a supplementary network of slower, more local service is needed as well. This also says to me that the idea of a "sealed corridor" is not quite going to work. While trains that exclusively run on high-speed routes may be able to be designed differently than others that need to mix with freights and go over grade crossings, their more heavily-built counterparts will still have to use high-speed lines in at least some cases. With current FRA regulations, they'll probably cause extra damage to occur to the rails, and will certainly cause a lot of operational headaches.

Another thing that I found interesting about the LGV network in particular was that the lines were almost never "straight". They had a very wide radius of curvature, but there's almost always a slight bend to the left or right. That contrasts with much of the (fairly flat) Midwest, where rails have historically been built in straight lines whenever possible, and then start curving when obstacles are encountered. I'm a bit curious why they decided to build that way—one guess is that it's to help keep train operators awake by always presenting a changing landscape.

European high-speed lines also get built next to highways fairly often, making use of leftover or relatively low-value land. This would seem to be a good idea in the U.S. as well, but American highways seem to be built with sharper curves most of the time. Certainly many curves could be rebuilt, but sprawling development often consumes land immediately adjacent to highways in this country and would make that a bit harder to accomplish.

(The map above is zoomed in to show a bit of "threading the needle" in France. You might find it interesting to zoom out and explore other parts of the European HSR network that I was able to map. A few segments aren't quite "true HSR", though, with speeds only up to about 100 mph in some spots.)


  1. It would be interesting to see which segments are upgrades and which are greenfield.

    Looking at your map I realize I've probably been on some high-speed routes without realizing it - if I remember right, the ICE in Germany is strongly branded (although not always high-speed, I think) but the French high-speed lines are more subtle. Or do I just not know French as well?

  2. Ps your maps are awesome - thanks for making them.

  3. Thanks Alex. Yeah, I think you're roughly right about the branding of service.

  4. I doubt keeping the drivers awake is an issue - it's not as if curves require the drivers to use a steering wheel. I would guess the reason is that LGV curves are built to permit trains to go at the maximum speed, including an extra factor allowing future speed increases. The minimum curve radius on the newest LGVs permits 400 km/h; there's no point in building wider curves than this.

    In addition, France is not as flat as the Midwest and Central Valley, so straight lines could require more engineering work. Note how CAHSR's greenfield segments, e.g. from the Central Valley spine to Pacheco Pass, are straight.