President Jacob Zuma has signed into law the Transport Laws and Related Matters Amendment Bill – paving the way for e-tolling, the Presidency said on Wednesday.

"The President... has, in terms of Section 84 (2) of the Constitution of the Republic of South Africa, 1996, signed the Transport Laws and Related Matters Amendment Bill into law," said spokesman Mac Maharaj.

"In effect, the Act will provide more effectively for the collection of toll; to amend the Cross-Border Road Transport Act, 1998 (Act No 4 of 1998), to empower the Cross-Border Road Transport Agency to collect toll on behalf of Sanral...."

The law in effect gives the South African National Roads Agency Limited (Sanral) the nod to put into effect e-tolling on Gauteng's freeways.

The signing came on the same day that the Supreme Court of Appeal was hearing argument in an attempt by the Opposition to Urban Tolling Alliance (Outa) to stop e-tolling in Gauteng.

The court was told that legislation allowed Sanral to explore options other than tolling to fund Gauteng's freeways.

It also heard that Sanral should, therefore, have kept an open mind about the matter, despite the Cabinet's approval of electronic tolling.

"Even bound by the Cabinet decision, they still had to follow the procedures of the act," said Mike Maritz, for Outa.

He argued that the Sanral Act allowed Sanral to explore other funding options. Sanral should have considered this and should not have been bound by Cabinet's decision that the project be funded with public money through e-tolling.

The High Court in Pretoria had granted Outa leave to appeal against a previous judgment, handed down in December, dismissing its bid to have the e-tolls scrapped.

Judge Fritz Brand asked whether Sanral should have ignored Cabinet's decision.

Maritz said Sanral should have kept an open mind and taken all options into consideration.

Last week, Transport Minister Dipuo Peters said the Gauteng Freeway Improvement Project would be implemented in 2013, but that a starting date had not been determined.

The e-tolls have been challenged by political parties and the Congress of South AfricanTrade Unions (Cosatu).

In April 2012, the High Court in Pretoria granted Outa an interdict approving a full judicial review before electronic tolling could be put into effect.

The interdict prevented Sanral from levying or collecting e-tolls, pending the outcome of a review. Sanral and the National Treasury appealed the court order.

In September last year, the Constitutional Court set aside the interim order, and in December, the High Court in Pretoria dismissed the application.

The court granted Outa leave on January 25 this year to take the matter to the Supreme Court of Appeal in Bloemfontein.