Using gravel routing in the Algarve recently, I discovered many delightful roads by trusting the c.t routing algorithm. The only hiccup was due to missing OSM tags on a truly impassable section. But of course there was a lot of variability in the quality of the passable dirt/gravel roads.
I added smoothness tags to a lot of rideable, but variable quality, dirt/gravel roads while touring. Later, I noticed that c.t does not use the smoothness tag (under the hood):
We use the surface= tag to determine how suitable a path is for cycling. We look for the values asphalt, paved, concrete, tarmac, paving_stones, compacted, gravel, ground, earth, cobblestone, grass, unpaved, dirt, and sand in roughly that order (the ones at the start are better). You can use the tracktype tag as an alternative.
Should I have used MTB:scale tags? I assume anything gravel-rideable is a 0 or 1 (maybe 2 in a pinch).
I think surface / tracktype tags do not give much information about actual gravel-rideability -- any of the surfaces listed above could be suitable for a gravel bike.
Is the smoothness tag useful?
Thanks.
Comments
Of course, as soon as I posted, I found this thread in which you explain that c.t does take smoothness into account.
Does the gravel algorithm also consider the smoothness tag?
c.t does indeed take smoothness into account – along with surface, tracktype, mtb:scale, sac_scale and anything it can lay its hands on!
smoothness is a slightly problematic tag because it’s quite subjective, and because it’s never really been explained whether it applies relative to the surface. (Is a ‘very_bad’ tarmac track better, worse, or the same as a ‘very_bad’ gravel track?) So the gravel weightings have to do a bit of a 2D calculation of smoothness vs surface. But if it’s there c.t will use it.
Thanks for the clarification. I will keep tagging 😀