If you don't live in the booming north, how do you feel about Canberra spending $600 million on the 13-kilometre stretch, part of the agreement ACT Labor reached with the Greens to form minority government?

That's the crux of the challenge facing the ACT government to sell this project as a winner, not a white elephant. Their reply centres on the benefits of high land values along the rail corridor and the likelihood of attracting more high-tech companies that see the value of easy access for their employees and clients.

According to Emma Thomas, project director at the Capital Metro Agency, ''this is far broader than just building a light rail''.

''I don't look at this as just a corridor to move people from Gungahlin to the city but something that can really turn the heat up on the whole of investment and industry in Canberra and give us better opportunities for employment,'' she says. ''We've already been voted as the most liveable city - this gives us another opportunity to really sell the benefits of that to people interstate and people internationally.''

However, the task of selling it is made harder by the perception Labor is going ahead only at the behest of the Greens and that the line is being built before the city masterplan is developed.

And then there are the critics of change, any change, and particularly of deviations from the original design of Walter Burley Griffin. Even though much of his plan was ignored, one facet that favours a light rail system is the wide boulevards, such as Northbourne Avenue, drawn up when heavy rail was in vogue and cars were unaffordable.

Further north, one glance at satellite photographs of Canberra over the years shows the phenomenal growth of Gungahlin. It is growing at five times the rate of other parts of the ACT, and is predicted to expand.

Hence the introduction of the Red Rapid bus service, running every 10 minutes from Gungahlin to DFO at Fyshwick via Russell and Barton between 7am and 9am, and then every 15 minutes until 7pm on weekdays. Even so, Northbourne Avenue is a car park during the morning peak hour.

In Canberra we suffer from car addiction, more so than any other capital city. Any why not, given the woeful state of public transport?

Herein lies the battle to get us on to public transport, with the Red Rapid a good first indicator.

If visiting Sydney or Melbourne, we are likely to head for public transport (because we know it works) but here, we are used to having the convenience of the car to run errands during the day and leave work whenever we want.

Light rail is being retrofitted to cities after being pulled out years ago. This week in Sydney, the light rail extension began operating from Lilyfield to Dulwich Hill.

Canberra's project has to learn from others, and keep in mind that Edinburgh's light rail took twice as long as planned and cost almost three times as much, for only half the line promised.

One solution for the traffic jam on Northbourne Avenue might be to knock down all the trees on the boulevard that marks the entrance to Canberra for travellers from Sydney and Melbourne, and have 12 lanes of traffic. Not a good look. And how long would it take for all lanes to be clogged?

Another solution is to retain the Red Rapid and install two tracks for light rail, aka trams, down the median strip, taking out some trees for the overhead wires.

''One thing is for certain - Northbourne Avenue will remain a boulevard of trees,'' Thomas says.

But the bus service may have to be halted to ensure the light rail is patronised as much as possible. That would mean if you work anywhere serviced by the Red Rapid except the city, you would have to get another bus - to Russell, Barton or Fyshwick - after the tram dropped you in Civic.

If we can afford it, the light rail should become a good option for a go-ahead city like Canberra. It will move people faster and should have lasting, city-wide benefits, according to the government.

Where a bus might take 100 passengers, a light rail car can carry 300, with the added benefit of unloading them quickly through multiple doors.

People are more inclined to walk further to catch the light rail than a bus, according to Thomas.

''People are confident in it, they know it will be there, they know it will take them to exactly where they want to go and it's regular,'' she says.

Thomas comes to Canberra after running the public transport system in Adelaide and being in charge of transport infrastructure projects in Brisbane. She is passionate about the project and has visited light rail in various cities, including the Gold Coast, where trams are already running without passengers and the system is due to become operational within months.

''[In Canberra] we have a car addiction that is quite significant compared to the rest of Australia,'' Thomas says. ''Part of that is our city design.''

She describes the Defence complex at Russell as a car park. ''That's not what I think the bush capital should be,'' she says. ''It should be something that's beyond a car park and we should get through our car addiction.''

Thomas sees an opportunity to redevelop Northbourne Avenue when property values rise along the rail corridor, as expected.

''For me, as someone new to Canberra and really enjoying Canberra, having that community housing in our face on Northbourne Avenue in the state that it's in - it needs some sort of uplift,'' she says. ''It's almost like a slum that Canberra has set up in the middle of the city.''

Why spend hundreds of millions of dollars on light rail instead of upgrading the buses or building more roads? Thomas says the car-driven cities of the United States keep building more freeways or ''car sewers'' that quickly become clogged.

''Gungahlin is the most rapidly growing centre in Canberra, with five times the growth of other regions within the capital, so we have pretty enormous population density out there and that's only forecast to continue,'' she says.

''What would Northbourne look like it if we didn't put in a solution? Could we build more lanes, would the median strip eventually be taken up to fit more lanes of traffic? … I don't think that's the right answer. We need another solution that moves vast quantities of people at once so we don't have everybody in their individual car taking up that space.

''France has very small cities that have light rail in them - Angers, Brest, Orleans, Dijon - all cities that are smaller than Canberra and still have light rail, around about the same length of track that we're talking about here.

''Portland has attracted so much attention because in a country like America, where the culture really is about cars, they managed to turn that culture on its head and they did that through believing in a light rail system and starting to connect people much better through that.''

The Gungahlin link is due to begin construction in 2016 and the masterplan, when completed, will consider linking Civic to the airport.

The debate over light rail for Canberra has been going on for decades.

In the mid-'90s, a report estimated the cost of a light rail system between Belconnen, Civic and Woden at $121 million. Nothing happened.

A decade ago, the Liberals were talking up another feasibility study but Labor's Simon Corbell, now Environment and Sustainable Development Minister, described the plan to revisit light rail as ''a load of rubbish''. The Labor government's feasibility study a decade ago concluded a light rail system would cost in excess of $700 million and could not be justified until the population reached between 450,000 and 500,000 people. In the interim, the report suggested building dedicated busways, to be converted later to light rail.

The Red Rapid demonstrates people will get the bus if it is reliable and convenient.

Liberal MLA Alistair Coe remains sceptical of building light rail, at least from Gungahlin.

''Even at the provisional cost of $614 million, that would be the single biggest capital works project the ACT government has embarked upon and to commit to such a project with such little knowledge about the economics, is very risky,'' he says. ''It is a political decision rather than a transport or economic decision.''

Coe says some jurisdictions are going ahead with bus lanes that, in time, can be upgraded to light rail.

''I'm told one of the most important aspects of planning a public transit system is to get the staging right,'' he says.

''In 2004 the ACT government commissioned KBR to do a study on light rail, including the staging options, and their determination was to do the Gungahlin-to-the-city leg last. In the Assembly last week, I asked what are the cost benefit ratios for the other legs in the network and they said they haven't got the figures.

''If they were serious about doing a system, they would be getting all the other legs, comparing them and then working out the appropriate staging.

''Otherwise they run the risk of blowing their money on the first route and never actually getting to the rest of Canberra. They are potentially doing a real disservice to light rail by going about it in an ad hoc manner.''

Coe says a light rail route running from Belconnen through the city and Russell to the airport would generate demand in both directions.

''There are employment hubs at both ends of the route and therefore you have people going in the train in both directions,'' he says. ''Now I'm not saying that would be more economic than what they're considering at the moment, but have they considered that?

''Where's the economic analysis to show Gungahlin to the city is going to be better for Canberra than Belconnen to the airport through the city?

''Only now are they considering a masterplan after they've made the decision [on Gungahlin].''

Coe is concerned that the Red Rapid route would be halted when light rail begins.

''From a financial point of view, what the government is potentially doing is replacing one of most profitable bus routes with a very unprofitable light rail route,'' he says. ''They have to [stop the bus route] and Emma Thomas told me that last week - that they couldn't have buses going parallel to the light rail.''

Barbara Norman, professor of urban and regional planning at the University of Canberra, backs the proposal.

"The building of light rail in Canberra is a very positive step forward,'' she says.

"I think we can afford it if we consider the long-term benefits to the community, as well as the initial costs.

"So if we take a broader view and a long-term view about our cost-benefit analysis, then I think it will be shown to be a significant positive contribution to the community.''

Norman said the light rail system would provide certainty for investment from industry.

''This enables people to have confidence to build medium-density developments and hopefully some innovative urban form flanking that area, which all is very consistent with creating a more healthy city.

"By doing Civic to Dickson and out to Gungahlin as a first step, I think, will be seen over time as one of relatively low-risk.

"Another way of framing the question is: Can we afford not to build it when we have 100,000 people out at Gungahlin and surrounds?''