Artist?s impression of the proposed Canberra light rail.

Artist's impression of the proposed Canberra light rail.

Canberra's centenary has helped start an interesting and important conversation about Canberra's urban form. Our first century as a planned city was broadly a success; but how will Canberra develop over its second hundred years?

The challenges for Canberra are well known. Our population is quickly heading towards 500,000 people. Canberra's urban boundary continues to expand, eating into rural and bushlands and increasing the headaches of urban sprawl. Continued dependency on car transport edges us closer to problematic levels of congestion and pollution. And Canberra is not immune from global pressures such as climate change and diminishing oil.

But as a young city, Canberra has an opportunity to respond to these challenges and to create a place that excels in liveability, sustainability and resilience. We're well placed to learn from the successes and failures of older cities. I recently took a few days out of a personal trip to the US for a study tour of Portland, Oregon.

Portland is widely regarded as being the ''greenest'' city in the US and a leader in innovative projects. One of its main attractions is its light rail and streetcar system, often cited as one of America's most successful.

On its surface Portland appears quite different to Canberra. It's obvious as soon as you disembark at the airport and a light rail service offers a $2 ride to the city. In fact, Portland has more than 100 kilometres of light rail and street cars. While Portland city has about 580,000 people, its surrounding region provides a base population of nearly two million - much greater than Canberra's.

Portland's cityscape is also much more urbanised than ours. This is especially true around the light rail corridors, which have attracted extensive development. Much of this development is built with a high level of aesthetic, social and environmental quality.

Different as it seems, elements of Portland provide a glimpse of Canberra's possible future. Several people who have experienced both Canberra and Portland told me that ''Canberra reminds me of Portland 15 or 20 years ago.''

Crucially, a central ingredient in Portland's recipe for success is its use of light rail as a positive, city-transforming tool. Its economy has grown. Its greenhouse gas emissions have dropped. The number of people walking, biking and using public transport has multiplied. Portland boasts that in a few decades it went ''from grey to green''. Could Canberra do the same?

Canberra is planning its first light rail line, from Gungahlin to Civic. Portland started building its first light rail in 1981. This followed a citizen-led ''freeway revolt''. Portlanders grew tired of traffic and expanding roads reducing their neighbourhood amenity. Over the following decades governments responded by building a network of light rail and streetcars and concentrating on ''human scale'' urban development.

This is the first lesson for Canberra. We shouldn't wait for congestion and urban decline to force us into sustainable transport solutions. We can start them now. Portland's planning U-turn didn't happen without opposition. Some people decried Portland's ''war on cars''. A former Portland mayor summed up the city's approach well. ''Portland didn't declare war on cars,'' he said. ''We just made the conscious decision not to surrender to them.''

Portland's decision-makers also worked hard to maximise community involvement. The government enshrined several planning principles to govern its projects. Number one is ''public involvement''. This is another lesson for Canberra. We must genuinely engage and involve the community in projects and leverage community knowledge and creativity.

Portland's light rail and streetcars are the heart of its positive urban transformation. The people I met in Portland's private, public and community sectors all recognised that transport and urban renewal projects were interdependent. At the city-wide level, fixed rail corridors have strategically directed the city's growth, helping keep sprawl at bay.

At the local level, Portland has taken advantage of these corridors by championing ''EcoDistricts'', a model of public-private partnership that emphasises district-level innovation in sustainability.

In Portland's ''Brewery district'', for example, the co-ordinated redevelopment of several blocks allowed a shared, district-wide cooling system that significantly improves the economic and environmental performance of the whole district. Key to EcoDistricts is the involvement of individuals and community groups, not just the big players of government and developers. Community groups and individuals often run district-wide initiatives such as energy efficiency or social programs.

This is an exciting and optimistic model of city co-operation where different groups contribute skills to produce an outcome greater than the sum of the parts. If we're smart we can take advantage of the same opportunities in Canberra as we undertake renewal along the light rail corridor.

Portland also serves as a reminder that light-rail related development should be used to multiply benefits for the community. Its neighbourhoods are littered with inspiring examples of community amenity, leveraged from the broader urban development. In Portland's Pearl District I visited a fantastic public fountain that doubled as a de facto swimming pool.

I visited a central and well-serviced affordable housing project, funded by Portland's urban renewal taxation scheme. It reserves 30 per cent of its revenue for ''affordable housing'' to ensure areas of urban renewal remain diverse communities. Solar panels and innovations such as roof gardens adorn developments all over Portland, a product of the city's environmental incentives, and a legacy that will give back to Portland's future generations.

While its built environment is impressive, Portland has also benefited from a unique city ''attitude''. It projects an image of a progressive city, a creative city, and a city open to new ideas. This has brought tangible rewards. It's known as a place for starting creative businesses. New and innovative industries, such as IT and clean energy are booming. My impression is that Canberra shares some of this progressive attitude.

Whether it is through our pioneering research work, digital development, our 40 per cent greenhouse gas reduction target or our same-sex marriage laws, Canberra's reputation is swelling. In a modern, competitive world, this sort of reputation is invaluable.

Despite its successes, don't think that Portland is a utopia. We can learn from its struggles as well as its successes. For example, Portland's transit mode share has grown quickly to about 16 per cent - about double Canberra's - but the rate of these gains has slowed recently. There are complex factors at work, but it reminds us that simply building a light rail line isn't a transport panacea. ''Active transport'' has been Portland's biggest contributor to reducing driving trips, a reminder that Canberra needs to keep growing support for walking and cycling.

I was also surprised by Portland's visible homeless population. Urban renewal isn't a magic bullet for complex social problems. As Canberra grows and changes we must redouble our efforts to make compassionate social policies. The built environment means nothing by itself; it is only there for people.

Canberra is a city that is changing quite quickly. This is a critical moment to absorb lessons from best practice cities. Portland tells us a lot about light rail's role in shaping a city to be more sustainable and people-friendly. It tells us about positive co-operation between governments, communities and private enterprise.

It reminds us that with the right efforts, cities can experience wide-scale urban improvement in a relatively short time. Canberra might be a different place, at a different scale, but there is nothing to stop us achieving these same outcomes.

Shane Rattenbury is the Minister for Territory and Municipal Services.