This is part of the Treforest Community Route and it joins up with the existing Church Village Community Route creating a lovely 6 mile traffic-free trail from Llantrisant to Treforest.
As this was once an old railway line maybe these archways were for the workers to take cover from passing carriages.
There are a couple of pieces of artwork along the way and below is one of them. Click and enlarge the notice board shot to see who they are. Many people will be familiar with one of the statues.