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We're building a U.S. street routing application (finding paths for cars between two or more locations using public roads) and would like to use open source data US Tiger Data or Open Street Map or other if available nationally.

We have worked extensively with the US Census Tiger Street Segment data before (we built a geocoder http://maplarge.com/geocoder using Tiger), and using the Tiger data is our preference. However, I'm missing two pieces of important data that I think should be there but I can't find them in the documentation:

Question 1: Direction: I know some streets segments are One-way, meaning that traffic is only allowed to flow in a particular direction, and I need to know if the Tiger or OSM have direction attribute data that can be linked to street segments. Specific links to documentation / data / examples would be awesome.

Question 2: Connectivity. When two roads cross it implies an intersection. However, you can't always go from one road to another.. for example, when a local road crosses a limited access highway, connectivity is often limited to certain "on ramps". I would like to know if the Census/OSM data can reliably provide information about connectivity at intersections. Specific links to documentation / data / examples would be awesome.

Thanks!

(ps this is a high volume application that requires our specific architecture, please don't dodge the question and suggest ArcGIS, MapPoint or a web service.)

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    MapQuest Open - have developed 'Open Directions' based on OSM data and there is an API available open.mapquestapi.com/directions – Mapperz Aug 2 '11 at 21:38
  • Thanks, that suggests the OSM data might be usable, but unfortunately they don't offer an explanation on their site and a web service api isn't going to work for us. – Glenn Aug 2 '11 at 21:49
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The Data is not quite there for what you require - but some is...

The TIGER Edited Map maybe of interest to you.

http://wiki.openstreetmap.org/wiki/TIGER_Edited_Map

enter image description here

Red areas are ways which have not been edited since the TIGER import.

Green areas are ways which have been edited.

There still is quite a large amount of fix up required for the TIGER data before it can be used. http://open.mapquestapi.com/tigerviewer/index.html?zoom=9&lat=40.07546&lon=-76.329999&layers=B

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oneway = 'yes' is how I understand flow direction limitations in OSM.

OSM shares nodes on intersecting ways. You can detect the ways by checking the reference ids of the nodes.

I have noticed that there are more than a few shared nodes at grade separated crossings which can cause some pretty serious routing issues.

Since much of OSM in the US was based upon a batch TIGER import, many intersections are based upon that data model. That is, if a motorway intersects any feature and doesn't share a node, then you can assume a grade separation. However, this is not always the case, unfortunately.

OSM has two related tags that indicate grade separation: - bridge = 'yes' and - layer = x (some number)

The bridge part is self explanatory. The layer tag indicates the z value of the particular road at the crossing.

  • Thanks Peter!. Also on the oneway tag, I noticed things are also more complex. Here are variants I have seen case "yes": case "true": case "1": case "-1": case "no": case "0": case "false": – Glenn Apr 3 '12 at 4:50

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