Skip intersection corners (stop-signs, traffic lights, etc)

[adamfranco]

Stops aren't fun, so intersections should be skipped in calculating curvature.

One mechanism to filter these is to look for adjoining nodes with highway=stop or highway=traffic_signals and ignore the curvature of the intersection.

Another technique that may work when highway=stop/traffic_signals nodes aren't provided is to calculate the angle between any triplet of nodes and exclude any angles tighter than some threshold -- e.g. ~90-degree and tighter corners made up of 3 nodes (not smoothed into a curve) are probably intersections.

[adamfranco]

Pau, France prior to roundabout change: Same view without roundabouts ways squashed to 0 curvature:

[adamfranco]

Phoenix Before:

After: