It's the [National Byway][1]. It's shown as purple on the cycle map. The relation through Cambridgeshire is [this one][2]. It's tagged as a "regional cycling network". See also their [website][3]. [1]: http://www.openstreetmap.org/way/311041338#map=16/52.1410/-0.0398&layers=C [2]: http://www.openstreetmap.org/relation/935883 [3]: http://www.thenationalbyway.org/

It's the [National Byway][1]. It's shown as purple on the cycle map. The relation through Cambridgeshire is [this one][2]. It's tagged as a "regional cycling network". See also their [website][3]. [1]: http://www.openstreetmap.org/way/311041338#map=16/52.1410/-0.0398&layers=C [2]: http://www.openstreetmap.org/relation/935883 [3]: http://www.thenationalbyway.org/