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I'm trying to identify the most appropriate "degree" of road in some areas. The wiki states that Secondary "nevertheless forming a link in the national route network." Is this actually a requirement? And on a related note, is the viable source of this information found on freeway exit signs? The area I'm looking at is here and has two road marked as as secondary, though the southern road (likely to have a national number and probably should be primary) is more prominent than the north. But I ca not imagine 256th having any national reference. My findings on unclassified vs tertiary suggest that they are the same where tertiary is a more prominent unclassified road. To which I think tertiary should be used when no road of higher importance can be identified. |
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In practice, all areas use whatever is most practical. In the US highway=motorway and highway=primary are the defaults for Interstates and US roads, but secondary roads are commonly used for state roads. In Canada, these are used for provincial roads You gave to remember that the original tagging guidelines were written with the UK in mind. The us road guidelines are on the wiki here and here. |
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For government information on the USA National road network visit http://www.fhwa.dot.gov/planning/national_highway_system/nhs_maps/ |
It might be worth asking on a US-specific channel such as the talk-us mailing list or IRC channel - you'll probably get answers from people there who don't read this site.