The board of the embattled South African National Road Agency Limited (Sanral) announced on Wednesday that it had appointed Koos Smit acting CE, following the surprise resignation of Nazir Alli a day earlier.

Smit, a civil engineer with more than three decades of roads experience, including being a member of the Sanral management team since 1998, is currently the group's engineering executive. In fact, he joined Sanral from the Department of Transport's (DoT's) Chief Directorate Roads, where he was construction and maintenance director from 1996 until the establishment of Sanral in 1998.

Between 1977 and 1998, Smith occupied various positions within the DoT, including being director of toll roads from 1995 to 1996. He is a professional engineer registered with the Engineering Council of South Africa.

Smit will take over from Alli on June 3 and would remain in that role while the board undertook a process to secure a permanent replacement for Alli.

"The board has every confidence that Mr Smit will ensure that the daily operations of Sanral continue at the high level for which the agency is known," the State-owned company said in a statement, adding that it would provide Smit with the support necessary to undertake the role "at this challenging time".

There were mixed reactions to Alli's resignation, with some welcoming the news and others expressing deep anxiety.

Alli had been CE of the agency since its inception in 1998 and, until recently, had been widely praised for the way he had overseen the development and maintenance of the 16 000-km national road network, including around 3 000 km of tolled roads.

Neither Alli nor the board had offered reasons for the resignation decision. But the board dismissed suggestions that Alli had been asked to step down in light of the controversy surrounding the implementation of e-tolling on Gauteng's motorways.

"He was not asked to resign," the board said in a statement.

Alli's letter of resignation "did not elaborate on the factors that influenced his decision" and the board "did not believe it necessary, in the circumstances, to try to explore with him his personal deliberations and reflections".

Meanwhile, Consulting Engineers South Africa (Cesa), which was "saddened" by the news of Alli's resignation, said careful consideration was required when seeking a replacement.

“Alli’s replacement needs to have both senior managerial as well technical skills in order to operate in such a complex and highly technical environment.” Cesa considers the retention of skills as critical to ensure the seamless operation of a very important entity," CE Graham Pirie said.