Light rail, loosely defined as a rapid-transit style urban rail transport network with lower speeds and capacity than heavy rail, is an enticing solution for a growing number of cities around the world.
With government transport budgets more strained than ever, global carbon emissions running rampant and many city centres becoming unbearably clogged, this lighter rapid transit option is attractive on several levels.
The argument for implementing modern light rail systems for urban transport is a convincing one. Environmentally, light rail and tram networks hold significant advantages over heavy rail and bus systems...
more... as most light rail vehicles are powered electrically, with no emissions at the point of use and a more efficient use of energy.
Light rail's pros and cons
Light rail scores highly in other areas, too. High passenger capacity and low overheads makes for comparatively inexpensive operating costs, and unlike heavy rail systems, light rail vehicles can integrate with existing transport infrastructure, minimising expense by allowing tracks to be laid alongside existing streets or road reserves.
Quieter operation and generally more appealing aesthetics also often makes light rail more palatable to a city's residents than its transport alternatives.
Factors such as these are the reason behind the Obama administration's U-turn on light rail in the US in 2010, making it easier for light rail projects to secure funding in cities across the country.
"We want to base our decisions on how much transit helps the environment, how much it improves development opportunities and how it makes our communities better places to live," said US Secretary of Transportation Ray LaHood during the announcement last year.
For US Representative Earl Blumenauer, who saw his native Portland's Streetcar light rail system unable to expand under the Bush administration's strict regulations, this decision is a major economic and ecological boon. "This means quicker and better funding for streetcars, light rail and bus projects that improve transportation, revive local economies and reduce global warming pollution," he said.
Implementing a major new light rail system in a city is not a risk-free venture, however. Initial construction costs can vary wildly depending on local conditions, such as the need for tunnelling in poor soil conditions, as well as underground or elevated sections.
While some light rail transit (LRT) systems can cost as little as $15 million a mile, difficult conditions can inflate that cost by ten times or more.
Seattle's Link light rail system, which has two lines operational and four planned for the future, has been the US' most expensive LRT project, reportedly costing approximately $179 million a mile.
Building a light rail system in a heavily populated area can also pose delicate social challenges.
Here we look into three high-profile light rail projects, each at a different stage of development and dealing with different challenges, to find out about light rail development in the modern age.