Brad, using Alaska as an example, these roads are in fact, compacted by vehicles driving on them. I have occasionally seen a power-roller or sheepsfoot roller used to compact rural roads but such specialized gear is mostly used during the building of larger highways. Typically a road is built up with different sized gravels on top of a geotextile base. The last, top-most layer is a mixture of fine-grained gravel, clay and normal soil which is bladed smooth by a power grader. If the top-layer is correctly composed, which depends somewhat on its proximity to a supply of the proper materials, such a road can be quite nice to drive on. However, rain will degrade that surface eventually and it will need to be resurfaced. This is done on a fairly regular basis, but not IMO often enough. And of course, they are dusty in dry weather and messy in wet weather. The best time by far for driving on them is in winter.
I have never seen any such road compacted with equipment after the first construction. The geotextile layer is critical to prevent heavy damage from frost heave. All unpaved roads are built with geotextile, even driveways, because otherwise they would simply sink out of sight in the spring thaws. I live in Thailand half the year and always think to myself how easy it is here to create a road. Simply scrape the area free of vegetation and large rocks, build a form, dump some concrete over wire mesh inside the form, smooth it a bit and you're done. Later on, do you need water for a home across the street? Just lay the pipe atop the concrete, put a ridge of asphalt or cement to hold it in place and you're all set. Water pipes in Alaska must be a minimum of 4-feet below grade. Hope this helps. On Mon, Jul 20, 2020 at 8:09 PM brad <bradha...@fastmail.com> wrote: > Hmmm, interesting. I'm not sure they compact very many roads around > here (CO). Maybe a regional difference. It seems like they put a thick > layer of gravel on and let the traffic compact it. Not fun to ride on > with a bike, or a motorcycle. > Do rocks tend to come to the surface of a compacted road and create a > ball bearing interface? If they grade it after initial construction, > do they subsequently compact it again too? > > On 7/19/20 9:27 PM, Kevin Kenny wrote: > > > > On Sun, Jul 19, 2020 at 9:29 PM brad <bradha...@fastmail.com > > <mailto:bradha...@fastmail.com>> wrote: > > > > Thanks for diving in. If it's a very minor unimproved road and > > not clearly service, I usually tag it track. I would suggest > > adding some indication of road quality. If it's an improved > > gravel road, I consider surface=gravel sufficient. If it's > > rougher than an improved gravel road, surface=unpaved (in my area > > the surface is usually a mix of dirt, rocks, gravel, so unpaved > > seems best), and smoothness=very_bad (high clearance), or > > horrible (4wd) > > [https://wiki.openstreetmap.org/wiki/Key:smoothness], or > > 4wd_only=yes . > > > > > > A nit: most 'improved' gravel roads are surface=compacted. 'gravel' > > is like rail ballast; a compacted surface ordinarily has a mix of fine > > gravel and even finer material such as sand, and is rolled. Americans > > will often refer to a compacted road as a 'dirt' or 'gravel' road but > > the difference is like night and day when you're driving on one! > > > > For the rougher stuff, 'smoothness' is essential. Consider also > > 'tracktype', which addresses more the firmness of the surface rather > > than its smoothness. A clay surface may be lovely in a dry season and > > impassable in a wet one, despite having a fast enough slump that the > > surface is deceptively smooth. > > > > Some National Forests separate Forest Highway (a regular access road) > > and Forest Road (usually a logging track, might be inaccessible in any > > given season, and often passable only to logging trucks and similar > > high-clearance off-road vehicles). I don't know if any of them overlay > > the numbering of the two systems. > > > > _Please_ create route relations! > > > _______________________________________________ > Talk-us mailing list > Talk-us@openstreetmap.org > https://lists.openstreetmap.org/listinfo/talk-us > -- Dave Swarthout Homer, Alaska Chiang Mai, Thailand Travel Blog at http://dswarthout.blogspot.com
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