There has been a significant increase of e-tag registrations in Gauteng, the SA National Roads Agency Ltd said on Wednesday.
Most of the registrations had taken place at mall outlets, it said in a statement.
The agency was unable to provide a figure but the Beeld reported that more than 350,000 e-tags had been registered for e-tolling.
Salahdin Yacoubi, chief executive of electronic toll collections, told the publication that between 5,000 and 10,000 people had registered daily in the past week.
E-tolling is set to go live on April 30.
Sanral gazetted new tariffs on Friday.
Alternate users (people without e-tags) will be charged R1.75/km, compared to the standard tariff of 30c/km for registered users.
It said the higher fee was because of the need to recover costs, including invoicing and debt collection.
On Tuesday, several organisations and political parties raised concerns about the tariffs and asked Sanral to postpone the launch.
The Congress of SA Trade Unions said it was planning a second strike against the system.