The course runs around the tarmac cycle track but at no point crosses it so there are no traffic concerns to worry about. The surface is a high quality gravel surface in the main with the odd patch of potentially muddy bits if they're wet but overall it's an excellent running surface and should produce some fast times.
The Fowlmead Challenge route is viewable on MapMyRun here.
There are slopes rather than hills, so its not totally flat, each loop has maybe 100 feet of elevation rise, but there are some lovely woods to run by, ponds, grasslands, wet lands and some wild life to spot too! If its wet there might be a chance of some mud but the trails are high quality and drain well.
The route is suitable for either road or trail shoes.