Police are urging visitors to the Brecon Beacons not to park illegally on the A470 route from south to mid Wales.
Dyfed-Powys Police is expecting large numbers of people to visit the Pen y Fan area because an endurance event istaking place over the weekend.
Officers will be patrolling to ensure the A470 clearway around Storey Arms, a popular starting point for an ascent of Pen y Fan, is kept free of parked cars.
Officers urged people to find other parking and routes up the mountain.
Sgt Owen Dillon, of Roads Policing Unit, said: “I anticipate a very busy period on the local roads this weekend and particularly in the area of Storey Arms. In addition to the large number of visitors I expect to walk up Pen y Fan, the Fan Dance event is taking place, bringing extra parking to the area.
“There are a number of alternative places to park your vehicles if visiting the Brecon Beacons, which still have good routes to Pen y Fan.”
He mentioned parking at locations including Cwm Gwdi or the Neuadd Valley as alternatives, as well as asking people to consider using the bus service available between Merthyr and Brecon, which stopped at Storey Arms.
“We will be continuing with police patrols of the Storey Arms area this weekend and will take action where it is required.
“Our priority is ensuring there are no obstructions on the A470 and that people observe the clearway and do not park on the road.
“We appreciate that the beautiful Brecon Beacons draw in thousands of walkers, and we encourage visitors to come and enjoy the region.
“We just ask that they do so safely, taking into consideration their own needs, that of other walkers, and other road users who also want to come and enjoy what Dyfed-Powys has to offer.”