In a city obsessed with building subways and LRTs, it’s still the basic bus that carries more than half of the TTC’s 1.7 million daily riders.

Most of those patrons are oblivious to the likelihood that the vehicle they’re riding has long exceeded its natural lifespan. Thanks to the TTC’s unique bus rebuild program, though, it looks and rides like a new bus.

“We’re one of the few transit operators that actually gets 18 years out of a bus,” said TTC spokesman Brad Ross.

Even though the TTC is extending the Spadina subway and a new underground LRT is being tunnelled, its bus fleet is also gaining ground as the workhorse of the system.

No subway on the weekend? No problem, shuttle buses to the rescue.

No LRT yet on Finch Ave.? New articulated buses will soon supplement the fleet.

By more than doubling the life of its vehicles, the TTC bus rebuild program has saved the city tens of millions of dollars since it was launched by former chief general manager David Gunn in 1995.

Most transit agencies outsource the work performed in Toronto by TTC mechanics, technicians, upholsters and other specialists. But the TTC has the skills and the facilities to rebuild its vehicles in-house at the Duncan and Harvey shops, tucked behind the fences of the Hillcrest yard on Bathurst St. near Dupont St.

“Because you’re into economies of scale here, it’s cheaper,” Ross said.

The scope of the rebuild program is massive. One bus — rebuilt from the running parts to the flooring and upholstery — is released back into service every day. There’s a limit on the number of buses that can be off the road at a given time, so the program is carefully scheduled.

This year, the TTC will rebuild 180 buses; next year, 240.

“I don’t think anybody can do this as competitively as we can, especially with 240 buses,” said Al Pritchard, TTC senior manager of shops.

The rebuild program is already remaking more than twice as many buses as when it was launched.

When Gunn arrived, “we hadn’t bought buses in a long time, and they were deteriorating,” Pritchard said.

“When you buy your fleet in batches, structural issues come in at the same time,” he said. “That’s where a planned approach (to rebuilding) came in.”

The Duncan shop is the surgical theatre of Toronto’s transit world. The patients are hoisted aloft, with their guts splayed beside them on frames custom-designed by a TTC employee to hold a bus engine.

Rebuilding a vehicle before it breaks down on the road prevents what Pritchard calls “catastrophic failure” — a breakdown that puts the bus beyond repair.

The TTC’s old GM buses didn’t have power steering, much less air conditioning and wheelchair accessibility. What they did have was staying power. The last of the buses purchased between 1959 and 1981 was retired less than two years ago.

They were rebuilt three, sometimes four times. Some of the parts were manufactured in the TTC’s Harvey shops. Others were stripped from a stockpile of hundreds of the Detroit-built engines stored at the Hillcrest yard. The two-stroke engines were used by the Canadian and U.S. military, so parts were still available to the TTC, according to Pritchard.

“Sometimes we had to strip four engines to rebuild one engine,” he said.

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Today’s heavier buses, made from stainless steel rather than more flexible mild steel, don’t have the same endurance.

TTC diesel bus engines don’t even last the anticipated nine years; they need rebuilding after six to 7.5 years. The hybrids are good for only about six, said Pritchard.

It costs about $175,000 and takes about eight days to rebuild one of the TTC’s Orion 7 buses, purchased between 2004 and 2005. Given that a bus costs about $550,000 to $750,000, the rebuild is significantly less expensive than buying newer models.

“Nothing is as good as brand new. But when we rebuild, you expect to last another six years,” he said.

With new buses designed to last between 12 and 17 years, most transit agencies have adopted a longer-life strategy.

But there are challenges. The brine the city uses to coat the roads before winter storms is more corrosive than the salt of yesteryear.

As a result, said Pritchard, “rods that used to last five to six years are lasting four.”

It’s the experts at the TTC’s Harvey shop that make the buses look shiny and new again. Stripped to their carcasses, the corrosion is assessed, parts repaired and replaced as necessary. Even the floor is stripped back to the plywood to have the industrial vinyl replaced and reglued along its seams, to prevent moisture from rotting the wood beneath.

To put a sheen on the repair work, there’s a paint and upholstery shop.

Outside Harvey are the vehicles that are too far gone — a bus with a back end ravaged by fire; another that suffered a catastrophic crash.

Both are stored and stripped for parts, however, Pritchard said.

“We want to make sure the city is getting its money’s worth.”