He said it was not a matter of ''turning the tap on or off'' in response to market conditions.

The export of commodities such as coal and iron ore to India and China helped increase Transnet rail freight to a record 201million tons last year. Revenue grew by more than a fifth last year, thanks to higher volumes, Transnet's results for the year to the end of March showed.

Molefe seemed unfazed by the effect an economic downturn might have on the planned R300-billion capital investment programme.

Disappointing jobs data in the US, more signs of a slowing in China's growth and weak sentiment in Europe moved commentators to reduce growth forecasts last week.

Lower growth means less appetite for South African commodities, which could put pressure on Transnet's revenue.

The company will use its revenue partly to fund the R300-billion capital investment programme.

Molefe said the programme was not about short-term cycles.

"It's a 30-year capital expenditure programme that we will try to execute in seven years."

At worst, he believes, Transnet will spend R50-billion less over the seven years. He said the programme has been ''stress-tested'' for that amount.

Strong revenue growth bumped up operational expenditure by almost 22% in the year. Net profit was 1.5% lower at R4.12-billion.

Molefe blamed the lower profit on the company's higher tax expenditure.

''It was not because of weaker operations,'' he said. ''We paid more tax because of our higher profitability.''

He said that the higher rate at which capital gains were taxed also affected the bottom line.