Wednesday, November 13, 2013

having a funny turn

We went over to see our friends Jenny and Jim at the weekend, since they're imminently going to be elbow-deep in nappies and arse cream and all manner of other baby-related stuff. They have also pushed the likely date of our next Munro-bagging trip back by a couple of years, but hey, I'm not bitter.

Anyway, Jenny and Jim live in Alton, which is one of those places there isn't a really obvious route to from Newport. I'm not saying it's difficult or awkward, just that once you get to junction 13 of the M4 there are a few routes you can take, all of roughly equal time and distance. You can carry on along to junction 11 and down the A33 (this is what Google Maps tends to recommend) or you can get off the M4 at junction 13 and then head down through Newbury and Basingstoke on the A339 (this is what Hazel's satnav tends to recommend) or you can get off at junction 13, carry on down the A34 and cut off to the east at any of a number of places as far down as the M3 (this is what we normally end up doing).

What we did on Saturday was get off the A34 at the junction with the A303, head east as far as the junction with the M3 and then cut across country through Axford and Ellisfield to Alton. Not a bad route, all in all, though almost certainly only fractionally different from any of the others. What makes it interesting is the extraordinary navigational contortions you have to go through to turn left from the southbound A34 onto the eastbound A303. Left turns, even between grade-separated dual carriageways, are normally the easiest ones; just bung in a slip road and you're done, but not here. Check it out:

As with all seemingly mad road design decisions of this sort, there's a bit of history involved here, not to mention geography. There was until recently a pub sitting right in the crook of the junction, in the northeast quadrant, where the south-to-east sliproad would have gone, and no doubt the proprietors were a bit dubious about having a sliproad ploughing through their garden. Add to that a couple of awkwardly-sited bridges making widening (to accommodate sliproads) difficult, some analysis of traffic volumes for each leg of the interchange (the assumption presumably was that traffic for points east along the A303 would have already taken the A339, this being before the building of the Newbury bypass in 1996) and probably a lack of budget for major earth-moving operations and we end up with the current colossal clusterfuck where the left turn involves a dizzying turn through 450 degrees (not to mention traversing two roundabouts) instead of the usual 90.

The splendid SABRE maps website and its even more splendid historical map database gives some interesting historical context. The junction started as just a little spur joining two roads together, then when traffic volume and speed started to make that a bit dangerous it was turned into a roundabout, and only in the 1980s did it mutate into the full spaghettified nightmare.

It's a bit ironic if the pub (which you can see marked on both maps) was a factor in not building the obvious road layout, since I would guess that it was precisely the decision to redraw the road layout that was the death knell for the pub's business. You can see from the pictures that in both of the first two configurations traffic in all four directions would pretty much have had to come past the pub's front door, or at least within sight of it, whereas in the new configuration the pub was relegated to being at the end of a little spur off a slip road in the shadow of a couple of bridges. Scarcely surprising then that business dried up and the pub closed in 2008, the site now being occupied by a scrap metal recycling centre.

Tempting as it is to imagine that they do, road planners don't actively set out to fuck things up, it's just that it's sometimes hard to piece together in retrospect all the constraints they were under at the time stuff was designed and implemented, most significantly the need to use what's already in place as the basis for any future developments. There's an interesting parallel between this sort of evolution and biological evolution, which operates under precisely the same sort of constraints. Magicking up new features from thin air is the sort of thing a "designer" might do, and therefore exactly what tends not to happen, features instead building on and amending stuff that's already there. The classic example of this is the 15-foot detour made by the recurrent laryngeal nerve in the neck of the giraffe.

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