The South African National Roads Agency Limited (Sanral) on Saturday said the country's economy would come to a standstill if Gauteng motorists refused to pay e-tolls.
The agency announced it would switch on e-toll gantries in two months' time.
This would be after a bill authorising the project passes through Parliament.
Sanral reassured motorists the tolling system would be much cheaper than they were led to believe.
The agency’s spokesperson Vusi Mona said studies conducted showed a majority of people would pay less than R100 a month to use the highways if they bought e-tags.
E-tolls opponents, including the Congress of South African Trade Unions (Cosatu) and the Opposition to Urban Tolling Alliance (Outa), vowed to make the system unworkable.
But Mona said the country's economy relied on Gauteng.
“The roads in Gauteng are very critical in the turning economic wheels. If Gauteng comes to a standstill because of congestion [on the roads] then the whole of South Africa will come to a standstill.”
Under the project, motorists are expected to fork out some 30cents per kilometre for the use of the province’s upgraded highways.
Cosatu continued its calls for motorists not to buy the e-tags.