Tony Keller is The Globe and Mail's editorial page editor.

If failure is a great teacher, then the fiasco known as the Union Pearson Express means that Ontario's Liberal government deserves immediate membership in Mensa.

On Tuesday, Queen's Park admitted that the UPX has so far been a bust, and offered up a new, less illogical business plan for Toronto's downtown-to-airport train, which has spent the past six months running nine-10ths empty. The train for the 1 per cent – yes, that really was its business plan, financed with half-a-billion taxpayer dollars – is being converted into public transit, which is what it should have been in the first place. This is progress.

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There are a lot of lessons to be taken from this failure, for a lot of people – chief among them the government in Ottawa, many of whose senior officials used to work at Queen's Park.

The federal Liberals won office in large part on a promise to double infrastructure spending over the next 10 years, to $125-billion. The theory, which a growing number of economists support, is that sound infrastructure investments can deliver long-term benefits for the economy, increasing efficiency, raising productivity and improving everyone's quality of life.

It's an idea I strongly agree with – in theory. But out here in the messy real world, I have one nagging worry, and you should too. Governments are good at spending money, but they're not always good at spending it well. And unless infrastructure money is well spent, the notion of an economic boost doesn't compute. Instead, you're building subways to nowhere and trains for no one – a recurring motif in Toronto transit history.

More than a decade ago, Ontario's government decided that it would be a good idea if Toronto had a train between downtown and Pearson International Airport. The federal government was pushing the idea too. It sounded reasonable enough on paper, and the train tracks were already there. And so, after the private sector said it couldn't see the business case, the UPX magically ended up at the top of the priority transit plan for Queen's Park and it's not-at-all-arm's-length transit agency, Metrolinx.

But somehow, in a city desperately in need of more and better mass transit, the plan for the UPX was not focused on building a train to serve Torontonians, and not on carrying commuters. Instead, it was about impressing occasional foreign visitors, particularly well-heeled ones. Metrolinx and the government somehow got it in their heads that what Toronto really needed was the Davos of trains.

Franz from Frankfurt, partner in an international consulting firm who flies to Toronto once a year, arriving rested after a night in the business cabin's lie-flat bed, was Metrolinx's fantasy date; sorry, fantasy passenger. They were a lot less interested in Sangeeta from Scarborough, who works at the airport and commutes there and back 500 times a year. And they were ‎actively hostile to Wendy from Weston, who commutes into the city every day, using a much slower route than the airport train. It was so important to get Franz downtown quickly and without contact with the hoi polloi that, in the initial plan, the UPX was to pass through Toronto's neighbourhoods without stopping. Why? Because World Class City, or something like that.

The UP Express even hired style guru Tyler Brûlé and his firm Winkreative to conjure up a look, feel and experience that, according to documents obtained last year by the Toronto Star, would "lure choice riders." There are greeters on the train and in the stations, sporting fashion-forward uniforms. The UPX has its own magazine, its own chief executive officer, layers of management, "executive quality seats" – and fewer riders than the Toronto Transit Commission's most underused bus routes.

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There seems to have been an obsession with everything but the bothersome subject of actual, local customers, who pay taxes, vote in elections and take public transit, or would if it were available.

The provincial government deserves credit for this much: It failed, but at least it failed fast. It has now slashed fares on the UPX, to levels in line with the TTC and GO Train service. And at the two stations between the airport and downtown, riders will be encouraged to use the train as commuters. It is trying to turn the gold-plated train into public transit. Ridership will rise; it might even get overcrowded.

All of which would be a very good thing: If you're going to subsidize transit, isn't it better to subsidize a service used by a lot of people, rather than one serving next to nobody?

The challenge for government is that taxpayer money isn't an infinite resource. So when a government chooses to build a Sheppard subway that isn't needed, or a Scarborough subway that doesn't make economic sense, or take as its transit starting point a SmartTrack line that was drawn on the back of a napkin during an election campaign – welcome to transit planning in Toronto, circa forever – it is saying that other things, possibly more economically and socially beneficial infrastructure projects, will not be built.

In the pantheon of government misspending, the UP Express barely rates a mention. Half a billion dollars? Pfft. That's nothing. But a half billion here and a half billion there and pretty soon, you're talking real money. And pretty soon, there's none left.