Been there....I was curious.    Still G13 (Fietspad)  traffic_sign. 
But your edits give more sense. I think the traffic_sign is misplaced. 
The parcours is still for public use.
https://www.mapillary.com/app/?lat=51.817015000000026&lng=4.748581638888936&z=17&pKey=902225873677026&focus=photo&x=0.8941041239560528&y=0.49896521273060795&zoom=1.8202247191011236

Here you can see the G13 traffic sign. I think for the parcours itself 

The gate at the Vogelaarsweg is allways open.
The next gate after the junction with the cycleparcours is allways closed.
The parking for the 'Skibaan' is  further south. 
Greetz,
eggie