The Johannesburg Metro Police Department (JMPD) has urged motorists to avoid several roads in Sandton and be on the lookout for coal trucks blocking roads during the EFF's protest action against Eskom.
The party is protesting against load shedding and the privatisation of the troubled power utility.
On Friday morning, several trucks blocked Katherine Street ahead of the march to Eskom's head office at Megawatt Park.
JMPD spokesperson Wayne Minnaar said there was heavy traffic in Sandton and advised motorists to stay away from Grayston Drive, Rivonia Road and Witkoppen Road until 15:00.
Minnaar said law enforcement agencies were monitoring the march.
The African Transformation Movement (ATM) is also joining the march. It supports the protest because it too has concerns about Eskom.
News24's political journalist Lizeka Tandwa is following the march and has spoken to several people, including the truck drivers.
Mandla Mngomezulu from the All Truck Drivers Foundation in Gauteng said the organisation supported the march.
Mngumezulu claimed: "They (Eskom) are not complying with labour laws. Most of the time, some companies are employing foreign nationals. As ATDF, we are asking even the EFF to support us so we can reduce unemployment," he said.
Mngomezelo added that the foundation was calling on Eskom to give tenders to complying companies.
He added: "You see, all these trucks coming here are owned by black South Africans but not being given tenders [by] Eskom. Only two companies are operating in Mpumalanga. We are saying Eskom [must] give tenders to companies which are owned by black [South Africans] because this Eskom belongs to South African citizens."