The Congress of South African Trade Unions (Cosatu) said the planned drive-slow against e-tolling in Ekurhuleni and Johannesburg will be the first of its kind.
The drive-slow is expected to bring traffic to virtual standstill.
The protest will be led by Cosatu, which said it would be the first of many such events.
Another drive-slow was expected to take place in Pretoria, but it was cancelled because permission to protest was not obtained.
The federation union said motorists will start to gather in Whiteville, Ekurhuleni and at Cosatu House in Braamfontein from 6am.
Major routes expected to be affected in Ekurhuleni include the N3, R24 east, R21 and the N12.
Nellmapius Drive in Centurion will also be affected.
Cosatu Gauteng Secretary Dumisani Dakile said in Johannesburg, the N1 north and several other roads in the city centre will be affected.
“From the M1 north to west to the N1, then south on the N1 because that is where the main gantries [for the e-tolls] are.”
Cosatu called on motorists to drive at 10 kilometres per hour with their headlights and hazards on.
It said the protest will last for several hours.
If the controversial system is implemented, Gauteng motorists will pay around 30 cents per kilometre to use the province’s upgraded highways.
The Opposition to Urban Tolling Alliance (Outa) has been at the forefront of the fight against the e-tolls.
Last week, Outa and the South African National Roads Agency Limited (Sanral) met in the North Gauteng High Court for the e-tolls judicial review.
Outa claims the public hearings into the tolls were not substantial.
Sanral, through its advocates, said Outa was misleading the public and it waited too late to act on the e-tolls.
The agency claims the project was announced several years back.
Judgment in the case has been reserved.