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Over at the Language Log, Geoffrey K. Pullum was quite reasonably ticked at the sign indicating that bike racks are “only on westbound Loop shuttles”; the loop is in fact a loop, and westbound buses go east as well before coming round again. Yes, clockwise and counter-clockwise are more accurate and easier to comprehend.

It’s also true that, as he noted in his follow-up, attempts to define ‘West’ and ‘East’ in a loop are not intuitive, nor is it at all clear which mapping would be meant by a sign describing ‘westbound Loop shuttles’.

However, in today’s note he is reminded of the fact that the clockwise loop is only clockwise from aboveground, while from the underground vantage it is counterclockwise. True, true, and it is, um, anthropocentric to ignore the gophers’ point of view. So. Well done, Geoffrey.

But there is no need to go crazy. Mr. Pullum states that “there is no general way to refer to the direction of travel in a directed loop that does not rely on knowing an orientation relative to the geography of the loop that can be agreed on by all observers.” Um, I think not. Now, I’m no topographer (I did have a sign that said I was, but I think Prof. Klotz took it away from me), so I won’t come up with any good mathematical sense. But surely, one of the shuttles runs on the inside of the loop and one on the outside; I hope they are driving on the right. Inside and outside do not depend on vantage, nor are they ambiguous. They also fit on a sign.

If you aren’t worried about the sign being legible, but are concerned that the lanes might not be consistent, there are other ways, depending on the vantage point of the driver rather than that of the viewer. The driver going in one direction (one would hope) keeps the ‘center’ to his left; the other driver keeps it on her right. If the center has a campanile or other prominent landmark, all the better, as you can call one the tower-on-the-driver’s-left shuttle, but we’re keeping it general, right? You could call one shuttle the left-turning shuttle and the other the right-turning shuttle; even the gophers should understand that the drivers are above ground and right-side-up, and when we talk about the shuttle turning left, we are talking about the driver’s left.

Oddly enough, I can easily imagine a situation where one version of the loop is intuitively called up-hill and the other down-hill, despite their obviously covering the same difference in elevation. If one covers the steepest slope uphill and the other covers it downhill, while meandering on the lower grades in the reverse, then the former one is clearly uphill. Mathematically nonsense, but practically sensible. I am guessing that’s the case in Mr. Pullum’s example, but I’ve never explored the terrain.

Of course a far more reasonable and historic solution is that adhered to by Boston and its environs. First of all, make everybody go to Park Street, even if they are going from Newton to Cambridge. Then, call all trains headed for Park Street ‘inbound’ and all headed away from Park Street ‘outbound’. Sure, everybody will waste lots of time, but we’ll all know where we are. And, as Francis Dahl observed more than fifty years ago, if any stranger on the train ever asks you a question of any kind, you can simply say ‘no, you have to go back to Park Street and change trains’.



Philly's SEPTA has the same radial pattern. Simple but often inconvenient.

In Baltimore, they routinely refer to the "inner loop" and "outer loop", which, as you note, seems unambiguous. In Philly, this doesn't work, since the "beltway" is formed by three different highways...

Inner and outer loop don't work if the tracks are stacked one on top of the other for the entire loop.

Center-on-your-left and center-on-your-right works unless the tracks are face to face, i.e. so the bottom of one train points at the bottom of the other.

As long as gravity is involved, though, you have an absolute "up", and so you can have an absolute "clockwise" relative to the direction of up (either "looking up" if you're gophers, or "looking down" if you're terranean). And gravity probably solves the wheel-to-wheel train problem too, as that's harder to do if there's gravity to contend with. :^)

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