Cosatu has threatened to remove toll gantries "nicely", occupy Gauteng streets, and block freeways on December 6 if it does not receive positive feedback on memorandums against e-tolling handed to several departments on Friday.
"We are not going to destroy them [gantries]. We are going to take them down nicely and give them to Sanral (SA National Roads Agency Limited)," said Johannes Clouw, the trade federation's Tshwane chairman.
Sanral has been at the forefront of the e-tolling project in Gauteng, but the Opposition to Urban Tolling Alliance (Outa) has brought a court application to have the project scrapped. The judgment is awaited.
Protesters in Pretoria and Johannesburg voiced their opposition to e-tolling during the two simultaneous marches.
The Congress of SA Trade Unions gave the departments of transport, finance, and housing until 5pm on Monday to respond to their demands.
An official at the National Treasury in Pretoria, Huntly Pringle, said they would do their best to give a reply by Monday.
The federation's provincial secretary Dumisane Dakile told a transport department official that if authorities were unable to demolish the gantries "Call us, we have capable comrades".
"If we don't get a response, we are marching on the freeways. Comrades, bring your bicycles, we have organised tractors," Dakile said.
"This action for today is just a warm up... We must brace ourselves for a series of actions... If they are not going to respond positively, we are going to occupy all the streets on December 6."
During the marches, Cosatu called for Sanral to be disbanded and a commission of inquiry to be launched into the e-tolling system.
"We want to know who are the beneficiaries, because they are milking us of billions and billions of rands every year," said Dakile.
"Voetsek e-tolls, voetsek," he shouted.
Cosatu General Secretary Zwelinzima Vavi supported the blockade call and said workers must get there early, even in their "smoking Toyotas".
"Go to the nearest e-toll gate and park that car there the whole day... We want the government to see where the power is," he said to cheers.
Vavi said money lost through corruption had to be retrieved and put towards building roads.
"This e-tolling thing is another way to steal from the poor."
Suggestions that people instead use taxis were "nonsense", as taxis were "moving coffins" he said, and challenged Gauteng premier Nomvula Mokonyane to use taxis herself.
"Don't be arrogant with power, because we as workers will take that power and then you will be ordinary people," Vavi added.
ANC Youth League acting president Ronald Lamola said people had the power to force the project to collapse by not buying e-tags.
"We encourage all South Africans not to buy the e-tags because this project is targeting to steal from the poor."
The league was disappointed at the small number of white people who took part in the march, because it affected all South Africans.
SA Communist Party Gauteng chairman Joe Mpisi said: "We have been oppressed by an apartheid government. We must not be oppressed by a democratic government.
"The Communist Party is with you. The Communist Party doesn't support the privatisation of roads."
By 3pm most protesters had dispersed.
Gauteng transport MEC Ismail Vadi acknowledged receiving a memorandum from protesters and said that even though people had a right to protest, nobody had the right to take the law into his own hands, as there were other channels to raise concerns.
"Law enforcement agencies, therefore, will be called upon to ensure that those who break the law are dealt with appropriately and within the prescripts of the Constitution," said Vadi.