Tuesday, 30 April 2013

Road alignments revisited

Here is the plot of road orientations in the British Isles, with the earlier problem with projection fixed.

As before, mappers seem to have a preference for tracing roads in a West-to-East direction. There also seems to be a preference among highway engineers for building roads along the main points of the compass, and a tendency to avoid roads at 45 degrees to the main points of the compass. The pattern is similar for all types of road.

With the exception of motorways, there is also a bit of a bulge at around 70 degree east of due north. I can't see why that should be, but given the volume of data that underlies this, it's unlikely to be a fluke, so there should be some rational explanation.

In the previous discussion there was a suggestion that mappers might provide more detailed traces for roads running horizontally (East-West, rather than North-South) but I can't see evidence of that in the data. The average length of road segments is much the same for all directions.

Anyway, for what it's worth, there it is. Not as interesting as the graph that had a fundamental error in it (unfortunately) - but hopefully a bit closer to reality.

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