It is a single project which, if it goes ahead, will cost almost three times South Africa's transport budget for this year.
By Justin Pearce
BBC News website, Johannesburg
Depending on who you believe, it will either revolutionise the way South Africans see public transport and tempt them away from gridlocked roads - or it will swallow public money while transporting only a handful of white-collar professionals.
Critics say the Gautrain will serve only an elite group of passengers
The Gautrain is intended to link Johannesburg - South Africa's economic hub - with the national capital, Tshwane (previously called Pretoria), 50km away in 40 minutes.
That would be a huge improvement on a journey that can take up to two hours by car when the traffic is particularly bad.
Pressure on the transport system will intensify when South Africa hosts the 2010 Football World Cup and proponents of the Gautrain see it as a way of moving visitors to and from the airport, their hotels and the match venues around Gauteng province.
On the way it will stop at the main commercial suburbs between the two city centres, and there will also be a branch to Johannesburg International Airport, which currently is not served by public ground transport.
In a country where passenger train services have been in a slow decline over the last few decades, the idea of a new railway route using new technology sounded like something out of science fiction.
But when the national treasury announced recently that the project was to cost government 20bn rand ($3bn) as opposed to the 7bn rand that had been spoken of previously, suddenly the Gautrain passed from science fiction into news headlines - and politicians started asking questions.
Matters were not helped by the fact that in the very same week that parliament's transport committee was discussing the Gautrain, commuters frustrated at delays started burning trains on the existing lines, with 26 carriages going up in flame in a single evening.
Jeremy Cronin, chairman of the parliamentary transport committee, pointed out the dangers of a mismatch between the large investment in the Gautrain alongside the neglect of the older services that serve poor, black suburbs.
The existing train service is in need of investment
"My concern is that every time a Metrorail train is late the very costly Gautrain will become a target for resentment," he said.
"If this thing goes ahead and fails, then we will have a very costly white elephant."
Mr Cronin is a member of the governing African National Congress. Not surprisingly, the opposition has been an even more vocal critic of the proposed spending on the Gautrain.
"The government is unable to properly maintain and rehabilitate the existing 23,000 km of tarred roads," Democratic Alliance transport spokesman Stuart Farrow said earlier this month.
"How is the public then expected to believe that 20bn rand spent on the Gautrain is in their best interest?"
The concerns from parliament followed a presentation by public transport expert Romano del Mistro, who argued that bus-only lanes could be added to the Johannesburg-Pretoria highway at a fraction of the cost of the Gautrain, while the bus journey on a traffic-free lane would be only marginally longer than on the proposed train.
Last week, the Gauteng provincial government declared that the Gautrain project would go ahead despite the parliamentary committee's reservations.
"The committee needs to do a bit more work," Gauteng's finance executive, Paul Mashitile, told a press conference.
"The project has taken many years and they need a bit more time to understand it."
He said national Finance Minister Trevor Manuel had given him the go-ahead for the project.
Mr Mashitile also tried to calm fears that the government would end up bailing out the Gautrain if costs overran even the current projection, saying that the public-private partnership model that was being used would protect the government from further financial risk.
"Once we sign on the dotted line with the preferred bidder, that is the cost," he said.
Answering accusations that the Gautrain would be a service for the rich, Gautrain project leader Jack van der Merwe assured journalists that the price would be affordable: around 60 cents (US$0.10) per kilometre.
"The cost is aimed at being the perceived cost of motoring: the direct cost of fuel plus some of the operating costs. We are targeting single occupancy car users."
Gauteng provincial officials are selling the Gautrain as the core of an integrated public transport system for the province, complemented in the short term by feeder bus routes, and maybe one day more railway lines.
"When you look at a holistic, integrated system... the Gautrain becomes a catalyst for that," provincial transport executive Ignatius Jacobs says.
Gauteng's commuters - whether the poor on their crumbling trains and the better-off stuck in traffic jams - would agree that a lot needs to be done.
The question is how to do it: whether the Gautrain will be the "catalyst" portrayed by Mr Jacobs or the "white elephant" that Mr Cronin fears.