Traffic moves along Highway 401 in Toronto on Jan. 3.Chris Young/The Canadian Press
When Ontario Premier Doug Ford vowed to build the world’s longest traffic tunnel under the busy stretch of Highway 401 that goes through Toronto, he presented few details about the project’s expected cost, scope or timeline. He suggested it wouldn’t cost “hundreds of billions,” and said a feasibility study would determine the tunnel’s length and price tag – but not deter him from building it.
Tunnel experts say the project Mr. Ford outlined would be bigger, and more expensive, than any other traffic tunnel project in the world, or any single infrastructure project in Canadian history. And traffic experts warn that anyone who expects such a megaproject to fix the city’s congestion headaches would be disappointed.
How much would a tunnel along Highway 401 from west of Mississauga into the middle of Scarborough, a distance of about 60 kilometres, actually cost?
The short answer is a lot.
Veteran tunnel engineer and project manager Brian Garrod, a past president of the Canadian Tunnelling Association, whose CV includes all the major subway tunnels built in Toronto over the past 30 years, said the most recent North American price comparison would be the State Route 99 Tunnel in Seattle. Completed in 2019, it is about 3.2 kilometres long and cost US$3.3-billion.
A longer tunnel would enjoy some economics of scale, so $1-billion per kilometre is a reasonable rough estimate for a project north of the border, said Mr. Gerrod, who earlier in his career worked on the Chunnel between Britain and France. (Mr. Gerrod is a tunnelling specialist at Hatch Ltd., but spoke to The Globe and Mail on behalf of the Canadian Tunnelling Association.)
Doug Ford’s proposed tunnel under Highway 401 is transparently political
This estimate means Mr. Ford’s idea could cost at least $60-billion, if built at the length he has suggested. That price tag would represent 60 per cent of the $100-billion provincial budget for all highway, road and public transit projects over the next 10 years.
However, the actual projected cost of Mr. Ford’s tunnel vision, at least as the Premier laid it out last week, could even be double this estimate, or more.
The Seattle tunnel has four traffic lanes, two lanes in each direction on top of each other in one double-decked tunnel. In Melbourne, a four-kilometre traffic tunnel project under construction consists of two tunnels that can carry three lanes each.
A project aimed at replicating the 401′s current maximum of 18 lanes – or, as Mr. Ford has suggested, including a transit line as well – could require two or three parallel tunnels, said Dean Brox, a tunnelling engineer and consultant based in Vancouver whose work includes road tunnels as well as mining and hydropower projects. That could multiply that $60-billion cost for a single tunnel into eye-watering territory.
Tunnel vision
Tunnel engineers say the SR99 Tunnel in Seattle, completed in 2019, provides a glimpse of what Ontario Premier Doug Ford has suggested should go under the stretch of the congested Highway 401 that runs through Toronto. The 3.2-kilometre Seattle tunnel, pictured in cross-section below, took six years to complete and required a five-storey boring machine to create a double-decked tunnel that is 16 metres in diameter. It can accommodate four lanes of traffic, two lanes in each direction on top each other. It cost about US$3.3-billion. But the comparison ends there: Mr. Ford has vowed to build a tunnel in Toronto that could be as long as 60 kilometres – much longer than any other traffic tunnel in the world – that runs under a highway already 18 lanes wide at its busiest point. He has also said it could include a transit line. Experts say this could require multiple parallel tunnels and cost tens of billions of dollars more.
Exit
corridor
Evacuation
doors
Traffic
flow
Traffic
flow
Utility
corridor
Ventilation
duct
MURAT YÜKSELIR / THE GLOBE AND MAIL, SOURCE:
WORLD ROAD ASSOCIATION
Tunnel vision
Tunnel engineers say the SR99 Tunnel in Seattle, completed in 2019, provides a glimpse of what Ontario Premier Doug Ford has suggested should go under the stretch of the congested Highway 401 that runs through Toronto. The 3.2-kilometre Seattle tunnel, pictured in cross-section below, took six years to complete and required a five-storey boring machine to create a double-decked tunnel that is 16 metres in diameter. It can accommodate four lanes of traffic, two lanes in each direction on top each other. It cost about US$3.3-billion. But the comparison ends there: Mr. Ford has vowed to build a tunnel in Toronto that could be as long as 60 kilometres – much longer than any other traffic tunnel in the world – that runs under a highway already 18 lanes wide at its busiest point. He has also said it could include a transit line. Experts say this could require multiple parallel tunnels and cost tens of billions of dollars more.
Exit
corridor
Evacuation
doors
Traffic flow
Traffic flow
Utility corridor
Ventilation duct
MURAT YÜKSELIR / THE GLOBE AND MAIL, SOURCE:
WORLD ROAD ASSOCIATION
Tunnel vision
Tunnel engineers say the SR99 Tunnel in Seattle, completed in 2019, provides a glimpse of what Ontario Premier Doug Ford has suggested should go under the stretch of the congested Highway 401 that runs through Toronto. The 3.2-kilometre Seattle tunnel, pictured in cross-section below, took six years to complete and required a five-storey boring machine to create a double-decked tunnel that is 16 metres in diameter. It can accommodate four lanes of traffic, two lanes in each direction on top each other. It cost about US$3.3-billion. But the comparison ends there: Mr. Ford has vowed to build a tunnel in Toronto that could be as long as 60 kilometres – much longer than any other traffic tunnel in the world – that runs under a highway already 18 lanes wide at its busiest point. He has also said it could include a transit line. Experts say this could require multiple parallel tunnels and cost tens of billions of dollars more.
Evacuation
doors
Traffic flow
Exit
corridor
Traffic flow
Utility
corridor
Ventilation duct
MURAT YÜKSELIR / THE GLOBE AND MAIL, SOURCE: WORLD ROAD ASSOCIATION
How would such a tunnel be built?
The Seattle project required what was at the time the largest tunnel boring machine in the world: 17.5 metres in diameter, which is as tall as a five-storey building.
These custom-made machines cost more than $100-million each, Mr. Garrod said. While the tunnels would naturally come near the surface at exits, they could be drilled as deep as 50 or 100 metres, down into the bedrock.
To build on and off ramps at intersections would require slower or more expensive excavation techniques, such as the use of spray concrete while digging out an exit, or “cut and cover,” which involves digging a trench from the surface, he said. Massive ventilation systems, needed to whisk all the tailpipe emissions away, can require 30 or 40-metres-high tower structures above ground.
How long would it take?
One tunnel boring machine can only chew through about 2.5 kilometres a year, Mr. Garrod said. But any such megaproject, he added, would likely be split into more manageable 15-kilometre chunks.
To finish one of these 15-kilometre portions would take six years of just tunnelling, he said, which could only start after the two-year process of readying a massive launch shaft for the machine at the surface.
Add to that two more years for actually building the road inside the tunnel, plus more complications from digging on and off ramps, and from installing sprinklers and electrical and ventilation systems.
So just a 15-kilometre section would require a decade of work at least, excluding the years it would take for design, environmental assessments and political battles over the project.
Mr. Brox said the government could build 10- or 15-kilometre sections concurrently, potentially using several boring machines, to get to Mr. Ford’s 60 kilometres.
But this would make the project the largest in the world by far, he said, requiring massive amounts of labour, including foreign workers, to get the job done.
“It would be essentially unprecedented,” Mr. Brox said. “I think we can safely say that.”
Would it help relieve traffic congestion?
Many traffic experts say, simply, no.
Expanding highway capacity in this way, traffic engineers say, means drivers who may now avoid the highway at peak times or entirely will jump behind the wheel and clog up any new lanes, a phenomenon known as “induced demand.” In as little as a year, many experts say, studies show that congestion comes back, bringing with it calls for even more new lanes.
Baher Abdulhai, an engineering professor at the University of Toronto and the director of the Toronto Intelligent Transportation Systems Centre, said tunnelling under the 401 would only further entrench the car-dependent pattern of development across the Greater Toronto Area.
“It’s cementing people in cars, so it’s not sustainable,” Prof. Abdulhai said. “If you have the money for all that, then why not build transit?”
Steven Farber, professor in department of human geography at the University of Toronto and director of Mobility Network, the university’s transportation research institute, said even a shorter tunnel doesn’t make sense under any portion of Highway 401.
In other parts of the world, he said, the tunnels are primarily very short segments that pass through urban centres, allowing for parkland or other benefits above ground.
“To try to do this underneath an existing highway without it having any benefits above ground is nonsensical,” he said. “You’re just adding highway lanes and not actually improving anything.”
With files from Laura Stone