Rating agency Moody's has changed the South African National Roads Agency Limited's (Sanral's) outlook from stable to negative, due to debt and decreased e-toll revenue.

"The change in outlook and lower BCA (Baseline Credit Assessment) reflect the decrease in Sanral's financial strength following weaker than expected e-toll revenue collection, and Sanral's plans to increase debt issuance," the rating agency said in a statement on Monday.

The non-payment of e-tolls increased following a decision by the provincial government to establish a panel to assess the impact of e-tolls in doing business -- which sparked speculation among the general public that the e-toll project may be abandoned, the organisation said.

"This caused e-toll revenue collections to drop by 38% from July to November 2014, which in turn led Sanral to revise downward its expected e-toll revenue for the fiscal year 2014/15 to R907-million, against R1.4-billion previously," Moody's said.

Last week, Gauteng premier David Makhura released the findings and recommendations made by a panel set up on July 17 to examine the economic and social impact of the Gauteng Freeway Improvement Project and the e-tolling system set up to fund it.

Makhura said Sanral would implement results from the e-toll advisory panel and the upcoming consultation processes.

Moody's said because e-toll revenue was planned to be the main contributor to reduce borrowing requirements and help improve cash flows, the lower than expected revenues would likely lead to an increase in Sanral's debt level.

"Moody's anticipates that Sanral's debt will increase more than expected and reach R44.1-billion by 31 March 2015, from R39.6-billion at 31 March 2014."

On Tuesday, Sanral said it was not surprised by the downgrade.

"The ratings agency had warned at the time of the previous two ratings in July and November 2014, that any failure by Sanral to generate e-toll revenue leading to deteriorating cash flows and growing borrowing needs would lead to a downgrade," Sanral said in a statement.

Sanral chief financial officer, Inge Mulder, said income dipped after the announcement of the e-toll review panel.

"We now await the outcome of the process led by Deputy President Cyril Ramaphosa on e-tolling to provide policy clarity as well as the funding model for the GFIP," Mulder said.