In reply to:

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Most of the maps that you would have to pay a lot of money for are nothing more than cleaned up tiger/line maps. They just added one-way street info and what intersections are a bridge or tunnel in real life.

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Yeah, but one ways become a lot more critical than you may think. We went through this with Kim Salo's mapping software. If one ways only affected things like driving in SF where there is a lot of one way streets, but the next street is most likely a one way in the other direction it wouldn't have been that big a deal. Where it became a real problem was freeway on/off ramps. Those are all oneways and the tiger data (apparently) doesn't know which way they are going or which side of the freeway it was attached to. The end result was that more often than not it would tell you to drive passed the offramp you wanted and then tell you to turn across traffic (on the freeway!) to exit via the onramp on the other side of the freeway. Not very helpful. IIRC that was another free dataset provided by one of the US bureaus (SDL, SDAL, something like that) with accurate one way info, but no street names that Kim was working with at one point. If somebody could manage to compine the two datasets accurately that would get you the one way info.

-Mike