Just like with the vertical index, the Speed Factor indicates how much slower you run on a trail compared to asphalt. The more technical the course – with rocks, tree roots, boulders, or river crossings – the higher the factor. This extra time comes on top of the vertical index. 

A Speed Factor of 1.10 means you are expected to need 10% more time than on asphalt, 1.20 means 20% more time.

We distinguish between a Speed Factor for dry and wet conditions. Some surfaces, such as sand, hardly slow down in the rain. Other courses, on the other hand, can become significantly slower and more technical due to mud, slippery rocks, and wet tree roots.