Subway stations evacuated because of ceiling cracks, a major thoroughfare shut down due to a giant pothole and a Quebec town severed in two after its only bridge was deemed unsafe.

Such is life following the collapse of an overpass north of Montreal last September that killed five people — suddenly no risk is worth taking with the province's aging infrastructure.

"If there is ever a threat to the safety of our citizens, we will make the investments necessary to not only ensure our safety, but our sense of safety as well," Montreal Mayor Gérald Tremblay said after a central section of the subway system was closed recently when workers noticed cracks in an adjacent underground tunnel.

But the question of how best to balance public fears and real risks is not as easily answered.

The residents of St-Lin, a town of 14,000 just north of Montreal, are among those now realizing that a zero-risk policy comes at a cost.

Locals face an 18-kilometre detour as workers take down and rebuild the town's lone bridge, after cracks were discovered below the water line.

The damage was so severe that Quebec Transport Department officials decided they couldn't wait for a temporary span to be built.

"Engineers working on bridges are certainly a lot more careful now," says St-Lin spokesperson Sylvain Martel of the decision to press ahead. 

News of creaky infrastructure has been de rigueur in Quebec recently.

A public inquiry into the overpass collapse has led to several alarming revelations, one of which prompted the Quebec government to ban heavy trucks from 135 bridges and overpasses pending safety inspections.

It has fed a sense of fear among Quebecers, 59 per cent of whom said in a recent Journal de Montréal poll that they are afraid of the province's overpasses.

'Infrastructure getting old': engineering prof

These fears were perhaps best underscored when, in early August, a bridge linking Montreal to Laval was shut for several hours during rush hour after a bus driver became alarmed about a 37-centimetre pothole.

"Our infrastructure is getting old, it is deteriorating, but not every structure will collapse," says Saeed Mirza, a civil engineering professor at McGill University.

Yet fears of another tragedy — such as the bridge collapse in Minneapolis — have morphed into a delicate policy question for governments.

Given that widespread concerns about infrastructure can be politically damaging, governments are keen to get the most from their massive investments.

That has meant a boon in engineering technologies that can at once help rehabilitate infrastructure and ease the public's fears.

"There's a huge market right now for technologies that can help you prioritize repairs," says Paul Johnston, president of Precarn, a non-profit corporation that manages research into intelligent systems.

Precarn recently teamed up with Montreal engineering firm Tisec and the University of Quebec at Trois-Rivières to develop an acoustics monitoring system that can detect cracks in concrete and steel bridges.

Analyzing infrastructure can be expensive and technology such as the acoustics monitoring system are meant as cost-effective ways of determining their structural integrity.

"If you want to have zero-risk then the cost is infinite — the more of these methods that you apply, the safer the structure is going to be," says Tisec president and materials engineer Robert Hay.

"Methods that we have and others that are available are obviously necessary to reduce the risk to those levels that the public is comfortable with."

Hay's monitoring systems have already been used on Montreal-area bridges, as well as on facilities in the U.S. and India.

Engineers must be accountable: expert

But while new technology and ramped up inspections can help quell public doubts, Mirza maintains that any genuine effort to reduce risk must begin with a different approach to the way infrastructure is built in the first place.

"Our present philosophy is design, build and forget," he says. "That should not be the case. An engineer must design any facility for its entire life cycle."

For Mirza, a designing engineer must take the responsibility of how a structure will be maintained after it's built. He calls the lack of advanced practical training for engineers and other technicians a "major problem" in North America.

"If you have a fear that a bridge going to collapse, what effect is that going to have on you psychologically?" he asks.

"We want our engineers and other people that are inspecting and operating these facilities to be properly trained so there is no risk in the use of the infrastructure."