The man overseeing Ottawa's light rail plan says the downtown tunnel will have to go far underground, as much as 35 metres or more than 100 feet. He says it's the challenges of an urban area.

"It allows us to get under the complicated utilities downtown. We minimize cost for the city by doing it that way," said John Jensen, the Ottawa rail implementation director.

Challenges include utilities and parking lots that are already underground, as well as the Rideau Canal.

Some people disagree with Jensen's theory, saying digging just below the surface would save taxpayers' money, and commuters' time.

"There were routes that would have been a lot closer to the street," says transit advocate David Jeanes.

The city says it will take people about two minutes to get from the rail platform to street level.

"They're estimating two and a half minutes, but in my experience it's more like five when you're at that depth," said Jeanes.

Other cities agree with Jensen's plan, if Ottawa makes commuters the priority.

"As long as there are good facilities, elevators and escalators, to bring people from ground level to the LRT. That's the key measure to put in place," said Joe Mihevc, chair of Toronto's Transit Commission.

Construction of the downtown tunnel is not expected to start until 2013.

With a report from CTV Ottawa's Catherine Lathem