Planning gravel routes: reading the surface data
The Moveee team
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Road route planning is largely a question of which roads are quiet. Gravel planning adds a second question that is much harder and much more consequential: what is the ground actually made of? The difference between a superb gravel loop and four hours of pushing a bike is usually a few hundred metres of surface nobody recorded.
Where surface data comes from
Nearly every routing tool you will use is built on OpenStreetMap, where roads and tracks carry tags describing them. The one that matters here is surface, and it is contributed by volunteers — which means coverage is excellent in some regions and almost non-existent in others.
Knowing the vocabulary is what lets you read a planner's colours sceptically rather than trusting them.
| Tag | Means | On a gravel bike |
|---|---|---|
asphalt · paved |
Sealed road | Any bike |
compacted |
Graded, rolled hardpack | The gravel ideal — fast on 35 mm |
fine_gravel |
Small, well-graded stones | Very rideable |
gravel |
Anything from hardpack to loose rock | The coin toss — could be either |
unpaved |
Nobody recorded what it is | Unknown. Treat with suspicion |
ground · dirt · earth |
Unsurfaced track | Fine when dry, awful when wet |
sand |
Sand | Walking, mostly |
mud |
Mud | Avoid at any tyre width |
cobblestone · sett |
Stone blocks | Rideable, punishing, slow in rain |
gravel itself, which covers everything from a rolled farm track to fist-sized loose rock. It is the least informative common tag and the one most likely to decide your day.
Four checks before you commit to a route
A huge share of tracks have no surface tag at all. An untagged path is not evidence of a good route or a bad one — it is evidence that nobody has been there with a survey app.
Two minutes of looking at aerial photos resolves most untagged sections. A pale, straight line through farmland is usually a decent track; a faint trace through a wood is usually not.
The tag that ruins a gravel route is rarely the surface. It is access=private, a locked gate, or a ford that is fine in August and impassable in March.
Unsurfaced tracks have a memory. A clay track that saw two days of rain is a different route from the same track after a dry fortnight, whatever the tag says.
Build in escape routes
The single most useful habit in gravel planning is not picking better tracks — it is making sure that every questionable section has a sealed road within a few kilometres. Then an unrideable surface costs you a detour rather than the day.
This matters most on the sections furthest from anywhere, which is precisely where surface data is thinnest and where a wrong guess is most expensive. Plan the remote parts on the surfaces you are most confident about, and save the experiments for the bits close to a road home.
Distance means something different
An 80 km gravel route is not an 80 km road route. Expect to be substantially slower for the same effort, expect climbs to be harder at the same gradient because traction and rolling resistance are worse, and expect to spend real time navigating rather than riding.
A rough planning rule: budget the time you would need for a road ride perhaps a third longer, and more in the wet. This has knock-on effects on food and water, because the shops are further apart too — how to plan a 200 km ride covers the resupply thinking, and it applies at shorter distances off-road.
Tyres and pressure do most of the work
Surface choice and tyre choice are the same decision approached from opposite ends. A 45 mm tyre at low pressure turns a lot of "coin toss" tracks into pleasant riding; a 32 mm at road pressures turns them into a fight. Tyre pressure for cyclists makes the case that most riders run far too much pressure, and nowhere is that more true than off-road — the impedance losses the article describes are dramatically larger on a rough surface.
If you are still deciding which bike the day belongs to at all, gravel vs road: choosing the right surface covers the training side of that choice.
Planning with surface in mind
Moveee's Route Engine reads the same OpenStreetMap surface data described above, so a route it builds knows the difference between a sealed valley road and an unsurfaced farm track rather than treating every line on the map as equivalent. That does not make the untagged sections knowable — nothing does — but it means the ones that are recorded get used properly.
And for the sections you genuinely cannot judge from a screen: ride out and back to them first, from the road end, on a short day. A reconnaissance ride is cheaper than discovering a 3 km sand section at hour four of a planned big day. Bikepacking route planning takes the same caution and applies it across several days.
Sources 5
Where this article summarises a study, the study itself is linked — not a write-up of it.
- 1 Key:surface — OpenStreetMap tag documentation · OpenStreetMap Wiki · 2024
- 2 Key:tracktype — OpenStreetMap tag documentation · OpenStreetMap Wiki · 2024
- 3 Key:access — OpenStreetMap tag documentation · OpenStreetMap Wiki · 2024
- 4 Barrington-Leigh C, Millard-Ball A The world's user-generated road map is more than 80% complete · PLoS ONE · 2017
- 5 Bertucci WM, Rogier S, Reiser RF Evaluation of aerodynamic and rolling resistances in mountain-bike field conditions · Journal of Sports Sciences · 2013
Build a route that is actually worth riding
The Route Engine works from real surface and elevation data and favours quiet roads, so it finds the lanes a fastest-way-there app routes you straight past. Give it a distance and a direction and it does the rest.
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