On Wed, Jul 21, 2010 at 10:12 AM, Stephen Woodbridge < wood...@swoodbridge.com> wrote:
> On Sat, Jul 17, 2010 at 10:52 PM, Alan Millar <a...@bolis.com <mailto: >> a...@bolis.com>> wrote: >> >> Am I really asking something unreasonable of a router that when an >> xxxx_link way meets an xxxx way at a very low angle, the router should >> know to go forward and not almost reverse? >> > > To some extent yes, this is unreasonable to ask of the router. While it is > not totally impossible to build a router to do this, routing algorithms do > not deal with geometry they only deal with connectivity. You have to have > geometry to deal with angles. While this could be added to the preprocessing > of the data into the graph file you would have to represent it as another > cost constraint or as a turn restriction and the router would need to be > "aware" of how to handle these. > > It is better to fix the data, period! > > You can not expect all routers to implement every weird hack to work around > all the weird data problems that various data sources have and might want > the router to handle. This is just not reasonable. > My concern is that the turn is not per-se illegal, it just isn't a good idea when there's traffic around. Under Florida statutes, a U-turn can be made outside the city so long as it "can be made in safety and without interfering with other traffic and unless such movement is not prohibited by posted traffic control signs". So my understanding is that this turn, absent a double-double yellow dividing median (which *is* present in the original example), would be legal. On the other hand, unless it's 3 AM and there aren't any other cars on the road, it probably can't "be made in safety and without interfering with other traffic". So, it seems to me that the only way to perfectly correctly handle this would at the point of the router.
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