Tens of thousands of trade unionists across South Africa are expected to march against new toll roads between Johannesburg and the capital Pretoria.
The Cosatu labour federation – which is organising the rallies – says the proposed system will hurt the poor.
The protests are also directed against the practice known as labour-brokering – when agencies hire workers at low wages and on short-term contracts.
The marches are expected to take place in 32 towns and cities.
"The tolls will put a burden on the poor," Cosatu (Congress of South African Trade Unions) Secretary General Zwelinzima Vavi told reporters ahead of the marches.
"We're saying to the government, we remain open to talk to you. Call us, we will come running to find a resolution," he added.
Cosatu says it expects as many as 100,000 people to join the protests nationwide.
The government first built motorways in and around Johannesburg for the 2010 football World Cup.
It says the construction was not free of cost, and it now wants the electronic toll road system to retrospectively finance these wide and smooth roads, the BBC's Milton Nkosi in Johannesburg reports.
The start of tolling has already been delayed several times, after companies warned the fees would raise the cost of doing business.