A group of people blocked the N2 near Khayelitsha in Cape Town with rocks and debris during a reported service delivery protest on Thursday morning.
The protest at Mew Way affected both the inbound and outbound lanes.
Reports were doing the rounds on social media of stone throwing on the highway.
The City of Cape Town Traffic Department's Maxine Bezuidenhout said the lanes from the R300 southbound ramp onto the N2 had to be closed.
"POPS [Public Order Policing] and other law enforcement agencies are monitoring the situation," police spokesperson Sergeant Noloyiso Rwexana said, adding the protesters were dispersed and no one was arrested.
It was not immediately clear what the grievances of the protesters were.