[Tagging] Turn Restriction usage

Stephen Hope slhope at gmail.com
Wed Apr 11 13:04:27 BST 2012

I've been clearing up some routing bugs reported in my area on Mapdust.
Some of them are valid errors, and I've fixed them. Some I'm not so sure

In one case there is a road where a two way section comes to a divider and
becomes two one way sections for a while. The suggested route came along
one of the one way sections, then turned about 340 degrees to go down the
other side of the road. It may be legal to do a u-turn there, but I don't
think it's safe, or even possible for most cars. I was thinking about it,
and many other divided road are similar where they split/join. Should we be
putting no u-turn restrictions on these? There's no actual signs.

The other thing I was wondering about is traffic lights.  Where I live, it
is illegal to do a u-turn at an intersection with traffic lights unless
there is a sign allowing you to. There's no signs saying not to, you're
just supposed to know. There has been some discussion in the past with
routers that have this sort of knowledge built in. Did anything come of
this, or should I just start putting four turn restriction relations on all
the traffic light intersections in my neighbourhood? That's going to be
painful, not to mention causing a lot of road splitting.

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