[Talk-us] Dirt Roads (formerly: Abandoned railway)

Bryce Nesbitt bryce2 at obviously.com
Sat Sep 6 05:24:44 UTC 2014

I see rural roads breaking down fairly neatly:

   - Paved
   - Unpaved improved
   - Track
      - ATV/Narrow vehicle only (the United States Forest Service defines
      this as 50" body width or less)
      - Single track (e.g. Motorcycle)
   - Trail
      - Closed to some combination of ATV/Bicycles/Stock/Motorcycles/etc.

Unpaved improved roads are suitable for general vehicle travel.
Tracks have exceptions, perhaps seasonally.

BUT ANY OF THESE can be primary, secondary, tertiary or residential.  Try
to tell an Alaskan resident that a gravel road can't be a primary highway,
and see what kind of reaction you get.   A primary challenge in using OSM
maps in the rural USA is that they're all classified as "residential" and
look like a spaghetti monster.  And that's misleading: there are rural main
roads, main tracks, and main paved roads.

And the term "4WD" never need come into it.  Tracks degrade primarily in
these ways.  And here there is no good tagging yet:

   - High clearance required
   - Limited traction when dry (e.g. sand)
   - Limited traction when wet (e.g. mud)
   - Narrow (e.g. must vehicles yield to cross in opposite directions)
   - Unusual conditions so noted (e.g. winch section).

The above are needed to determine if a given road is potentially suitable
for 2WD travel by a skilled driver.

One data source in the USA is the yearly MUVM maps (
http://en.wikipedia.org/wiki/Motor_Vehicle_Use_Map ) published by the USDA
under 36 CFR 212.56. See
These also specify closure dates for roads, or closure conditions.
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