THE world's longest train is operated by a single driver and an assistant, using a world-class computer programme, a thick file detailing every kilometre of the 861km trip it makes, and painted markings on power pylons lining the track from Sishen to Saldanha.

The cabin of the front locomotive, where computers play a critical role in controlling the acceleration, idling and braking of various parts of the train, is surprisingly spacious and comfortable. The new 15E locomotive, an addition to the line, gives an astonishingly quiet and smooth ride. It is the pride of Transnet Freight Rail.

It is from here that the driver - carefully selected from Transnet's veteran drivers - controls all the electric and diesel engines interspersed between three sets of 114 wagons to haul iron ore to the coast.

The driver-operated computer system allows the driver to idle or apply brakes on certain locomotive sets behind him and keep the locomotives at the back of the train continually nudging the entire train into a compact unit so it does not pull apart.

There is 34m of play between all the wagons, meaning when the train pulls off, the lead locomotive will travel that distance before the last wagon starts moving.

This makes controlling the train through valleys and hills, which a train of that length will do at the same time, an immensely complicated business that needs the driver's full attention as he slows, idles or accelerates various parts of the train.

The driver sits in a sprung, padded chair. Four computer screens, buttons and levers are within easy reach. The cabin is crisply air conditioned in an environment when the ambient temperature regularly tops 40° C in summer.

The cabin is fitted with a small fridge, a hotplate and a microwave oven, making a demanding just that bit more comfortable, driver Riaan Thiart says.

"This is the Rolls Royce of locomotives. It's brilliant. You can't really compare this to the other locomotives because it is so state of the art," Mr Thiart says as he taps the "vigilance" button that acts as a "dead man switch" on the train.

If for any reason he does not respond to its irregular prompts within a minute or so, the train will automatically come to a stop. It takes 1,2km to bring a train this size to a halt from its top speed of 60km/h fully loaded, but an emergency stop can be made in 380m, Mr Thiart says.

The line, which unlike conventional lines is a solid welded rail without regular breaks to accommodate expansion and contraction from heat and cold, is regularly patrolled by ordinary trucks fitted with steel wheels in addition to their rubber ones to check the quality of the line.

Mr Thiart's train departed Kumba Iron Ore's Sishen mine on schedule. Within hours it passed two empty trains waiting at loops for spaces at Sishen and Assmang's Khumani mine.

At Sishen there are three loaders, each with three flasks containing 33 tons of ore that are systematically dropped into empty wagons passing slowly underneath them.

The critical aspect is to load the correct weight - 100 tons - and to have the load perfectly balanced to avoid the wagon being pulled out of line by Transnet for fear of it jeopardising the rest of the load on the 21-hour trip.

Safety measures and well-maintained equipment were the main factors in improving the reliability of the service, says Norman van Wyk, Transnet Freight Rail's operations manager, adding there was a new purpose in Transnet in the past five years as new, dynamic people joined the parastatal and found new ways of improving service.

"Since 2008 when we implemented this long train everything has changed on this ore line. We brought in new technology on the locos, extra loops, new signalling systems and new-generation electric locomotives, we converted yard automation to electronically operated points.

"We installed a lot of wayside monitoring technology and weigh bridges, wheel impact monitory, acoustic bearing detectors. There is a complete change of focus in the way we run the business. And to assist us to run it safely we brought in all this technology. Safety is our priority," Mr van Wyk says.

The changes are clearly having an effect. A record 52,3-million tons were railed in the year to end-March.

The ore line reached another record, this time in weekly tonnages of 1,222-million tons earlier this year, up from the previous high of 1,147-million tons in September of last year.

Mr van Wyk concedes that with the exception of the coal line from Mpumalanga to Richards Bay there was much that still needed to be done on other lines, like the railway running from the manganese fields in the Northern Cape to the east coast harbour of Port Elizabeth.

The capacity on the iron ore line and current rolling stock is 62-million tons. A feasibility study is under way to see how and if the system can be upgraded to 83-million tons.