How roads are scored
The same explanation the app gives under the ⓘ beside every score.
TwistyDrives gives every road a twist score, and the score is the app's one idea: a number that says how much of a road is corners, worked out the same way for every road on earth. This page says what the number measures, how to compare roads of different lengths, what the five colours on the map mean, and what the score cannot tell you.
What the score measures
Every bend is measured from the shape of the road on OpenStreetMap: the radius of the curve. A sweeper, 60 to 175 m, counts once; a tight corner, 30 to 60 m, twice; a hairpin, under 30 m, four times; a straight not at all. Each stretch’s length in metres, times its weight, added up, is the road’s curvature.
The 0 to 100 twist score sets that total on a scale where 100 is corners end to end and 0 is straight. Longer roads and routes score higher, because every corner is added up, so a whole route will outscore any one road on it.
Twist per km
Twist per km divides the same total by the length: the cornering in each kilometre, whatever the length. 100 twist/km is the equivalent of a hundred metres of sweeper, or fifty of tight corner, in every kilometre. It is the fair way to compare a short road with a long one, and it is what “Prefer twisty roads” ranks routes by.
| Under 50 | Mostly straight, a bend now and then. |
|---|---|
| 100 to 200 | A proper drive, cornering most of the way. |
| 300 and up | Hard work. |
| 1,000 | One long sweeper with nothing straight in it. |
The five bands
A road’s band comes from its total curvature, so a long winding road can reach a higher band than any one part of it. These five colours are for whole roads: the lines on the map, the bar beside a road’s name, the rows in a list. From least to most:
- Mostly straight
- Some corners
- Winding
- Destination
- Epic
The corner map
A road’s corner map uses a different scale, for single bends rather than whole roads, so its colours are not the bands’. A road in the yellow band, Mostly straight, is mostly green on its corner map. Tap a bend for its radius.
- Straight
- Sweeper
- Tight corner
- Hairpin
What it cannot tell you
The shape comes from OpenStreetMap, read about every 20 metres, so a kink shorter than that can be missed and a poorly mapped road scores poorly. Surfaces are as mapped, not checked. Junctions are left out of the score. Use it to decide where to look, then drive the road as you find it.
Road data © OpenStreetMap contributors, under the Open Database Licence. The scoring method follows the one published by the open-source Curvature project; TwistyDrives implements it in its own code.