In a commitment to drastic emissions reductions, 240 members worldwide, including the major railways of Europe, China, Russia, India and the US committed to a 50% increase in rail's share of passenger transportation by 2030.

The pledge is one of the top priority targets of the Low-Carbon Sustainable Rail Transport Challenge, launched by The International Union of Railways (UIC) and participant member states in December 2015.

The shift from heavy-polluting means of transportation such as road and air is needed to cut energy-related CO2 emissions by more than half by 2050, and limit average global temperature increase to 2°C.

But while many countries can work towards shifting public perception to embrace transportation systems already in place, the case is different for the US, where access to public transportation is severely restricted.

The sheer lack of a well-connected railway network dissuades daily commuters from taking the train to their workplace, while those looking to travel to another city are best served by fairly affordable and frequent plane connections.

The US is currently the world leader in urban passenger transport emissions, with 670 megatons of CO2 produced annually and the anticipated surge in population could make this much worse. By 2045, America's population is expected to grow by 70 million, with 75% of people concentrated around mega-regions.

Without intervention, this increased demand is bound to put great pressure on the economy. According to a report by US association Business Roundtable, subpar performance and the failure to invest in America's passenger rail infrastructure could cost $570bn in 2020 and more than $1tn by 2040.

But why have railways been relegated as a secondary means of transport by the American public and an unworthy financial pursuit by federal bodies while in other countries they are held up as the most promising means of sustainable mass transit?

Why don't Americans ride trains?

For the American public, emulating the European model for rail transportation is not as straightforward as it may seem. With much bigger distances, and longer travelling times between metropolitan areas, intercity train travel is also rendered less practical by low population densities across many regions.

Alongside the geographical hurdles, a long history of underinvestment and political animosity towards rail projects has also led to today's poor infrastructure and scarce connections.

A report published in February 2015 by the National Association of Railroad Passengers (NARP) shows a vast backlog of undelivered rail projects totalling almost $209bn. The document identified 274 projects, of which "some [...] represent competing visions for the development of the US rail network, incremental upgrades to existing service versus cutting edge rail technology."

The Department of Transportation (DOT) estimates that improving the condition and performance of the transportation system will cost $43bn, according to their Beyond 2045 analysis, while current annual capital spending is just over $17bn.

"Unlike highways, transit, and aviation, passenger rail lacks a source of predictable, dedicated funding."

"Unlike highways, transit, and aviation, passenger rail lacks a source of predictable, dedicated funding," the report reads.

As a result, airlines have secured their place on the market, offering widely available 24-hour connections between states, sometimes at cheaper prices than train tickets. Last year, rumours circulated that Southwest Airlines even lobbied against a high-speed rail project in Texas, an accusation which the airline denied at the time.

Rail projects in America have also been heavy politicised, maybe much more so than anywhere else in the world. According to the Economist, "opposition to rail is now often seen as essentially conservative, and Republican governors oppose rail projects to boost their conservative image."

Lessons from the greener cities of Europe

Speaking at last year's Rail Forum Europe, Transnev Group CEO Jean-Marc Janaillac said that "modal shift to rail would be key to make transport more sustainable".

Janaillac's claim certainly enjoys scientific backing. Figures released by the international public transport organisation UITP showed that in an urban context, the energy consumption of rail is seven times less than that of an average car.

Similarly, research by The University of California, Davis, and the Institute for Transportation and Development Policy maintains that if public transportations systems were to be expanded globally, approximately 1.7 gigatons of CO2 could be eliminated each year. This would mean a 40% reduction in urban passenger transport emissions by 2050.

A good example of how this approach can work comes from Europe, where every year 26 billion journeys are made on the rail system, while only 800 million journeys are made by plane. As such, total urban rail energy consumption is roughly 11,000GWh per year, comparable to the residential energy consumption of approximately one million people.

Highlighted by the C40 Cities Climate Leadership Group, a network of the world's megacities committed to addressing climate change, the Hammarby Sjöstad redevelopment project in southern Stockholm is a case in point.

Build originally as a host site for the 2004 Olympics, the area was later redeveloped into an environmentally sustainable, mixed-use district home to 20,000 residents, with good public transit connections. According to The Institute for Transportation and Development Policy, only 21% of trips made by its residents are by car, while 52% are by public transportation. The result is that CO2 emissions from transport by car are more than 50% lower in Hammarby Sjöstad than in the surrounding districts, and GHG emissions from buildings are 40-46% lower.

Advancing a new era of rail in the US

America's negative approach to rail investment has unavoidably led to a deteriorating system. DOT statistics show that 17% of the underlying structures of urban rail transit such as tracks, ties, switches and tunnels, as well as 19% of rail transit systems like power, communication and train control equipment are in poor condition.

Despite this, demand spurred by rapid population increase is already putting the system under strain. A new age of e-ticketing and improved broadband access on the railways is also driving popularity amongst the younger generation, with the numbers of rail passengers growing steadily year-on-year.

According to a survey organised by Global Strategy Group, 54% of millenials across ten major US cities said they would consider moving if another city had more and better transit options and 47% of them would give up their cars if their city had robust public transportation.

"54% of millenials would consider moving if another city had more and better transit options."

More recently however, the government seems to have woken up the realities of their railways.

After much controversy and backtracking, America's first high-speed railway promises to be complete in 2029. The first phase of California's high-speed rail is a 220mph, $68.4bn bullet train aiming to connect Los Angeles to San Francisco in just two hours and 40 minutes.

According to ECOPASSENGER, an online tool calculating the emissions of different modes of transportation, a trip between London and Edinburgh, the equivalent distance of around 350 miles between Los Angeles and San Francisco, would release 131% less CO2 if the trip was made by train rather than plane. The plane journey would also consume 90% more energy, as well as releasing much greater levels of other harmful emissions, such as particulate matter and nitrogen oxides.

In addition to its first high-speed line, in June 2015 the US Government introduced the Railroad Reform, Enhancement, and Efficiency Act, which provides $9bn for Amtrak between 2016 and 2019. The act was introduced following the derailment of an Amtrak train in Philadelphia which killed eight passengers.

Growing ridership indicates a promising trend

Going forward, DOT encourages setting up a "predictable dedicated funding source for rail projects" in the future.

For now, America's relationship with rail is certainly improving. Over the past few decades, annual ridership has grown consistently and now intercity routes welcome 30 million passengers on a yearly basis, with a particular strong outlook for mega-regions such as the Northeast Corridor, the Chicago Hub area, and the West Coast.

Even amid shrinking petrol prices, people continue to use public transportation. Commuters are also slowly waking up to their own financial benefits of leaving their cars behind. Statistics compiled by the American Public Transportation Association in January 2016 show that commuters switching from private to public transportation can save an average of $9,162 each year.

With the arrival of new lines, a steady stream of rail-focused funding and a shift in cultural and behavioural norms amongst passengers, it certainly seems that Americans could finally be persuaded to incorporate railway travel into their everyday lives, and in the process, become part of the solution to the global threat of climate change.