Telecommuting, HOV lanes and drive-through emission testing once seemed like the future of green transportation. To keep pace with growing mobility demands worldwide, recent efforts to reduce greenhouse gases and dependence on fossil fuels have shifted into high gear.

Such energy-saving alternatives as car sharing -- including Flexcar and Zipcar operations -- Smart cars, electric plug-in hybrids, biofuels and even drive-through battery recharging stations are no longer a pipe dream.

The future of green transportation promises to combine innovations in technology with higher performance standards and continued government policy change.

“During the past decade how high energy prices have gone has driven consumer demand for fuel-efficient hybrids and plug in cars,” says Deron Lovaas, federal transportation policy director for the Natural Resources Defense Council (NRDC), an international environmental advocacy group.

“There are a huge number of cars that need to be designed as fuel efficient and as low polluting as possible.”

Countries in the European Union, Japan and China are raising the bar on performance standards, while the United States is catching up, Lovaas says.

If it takes 15 years in the U.S. to turn over a fleet of new vehicles – longer for airplanes – and we’re already several years into that process, oil demand could possibly flat-line here within the next decade, Lovaas says.

The International Energy Agency reported last year that while oil remains the leading fuel choice worldwide, demand will peak just before 2020 and decline in 2035. Meanwhile, renewables and nuclear will double their current combined share in 2035, according to the IEA’s World Energy Outlook 2010.

“It’s hard to picture a total replacement any time soon,” Lovaas says. But in 20 years, a dramatic spike in oil prices won’t be so debilitating. Consumers will just switch to a different fuel source, he says.

“The dominant transportation fuels of the future will be a mix of biofuels, electricity and hydrogen,” according to Two Billion Cars by Daniel Sperling and Deborah Gordon. The 2009 book predicts vehicle ownership will double worldwide in the next two decades.

Transportation is one of the main sources of global warming pollution, smog, carbon monoxide and harmful particles that can cause asthma and other respiratory illnesses, cancer and other health problems, NRDC reports.

About one-third of U.S. carbon dioxide emissions, and 23 percent of global emissions are caused by transportation, according to several environmental group estimates.

In terms of freight shipping, the United States has an advantage over Europe, Lovaas says. “We rely on freight rail more than Europe. They rely on passenger rail.”

Many countries in Europe have high-speed rail networks, fast trains or bullet trains that travel more than 200 miles per hour.

Car sharing is another choice for urban residents who don’t necessarily need to own a car. The concept began in Europe and is most common there. Still, most large cities in the U.S. and Canada, along with hundreds of college campuses, also have car sharing programs today. Similar to a rental contract, the membership-based service provides access to a network of energy-efficient vehicles. 

In the future, we might also see more battery charging and switching stations such as those operated by Better Place, which began in California in 2007. A member’s maintenance plan includes use of quick-stop battery charging and replacement stations.

Other advances on the transportation front include the first U.S. performance standards for medium- and heavy-duty vehicles, announced late last year. The vehicles are the transportation segment’s second largest oil consumer and contributor to greenhouse gas emissions, according to the U.S. Environmental Protection Agency and the Office of Transportation and Air Quality. The groups are overseeing the new standards, which affect vehicles sold between 2014 and 2018.

Surface transportation is a lot easier to transition than airplanes, Lovaas says. Because of their size and design, it wouldn’t be efficient or safe to fuel airplanes with gas or electricity. “They are very liquid fuel reliant.”

The biggest progress in air travel will come from improved aerodynamic designing, satellite-based routing systems, redirecting some freight to intercity rail, and use of biofuels, which come from plant-based alternatives such as sugar, corn, grass, even algae. Ethanol is the most common biofuel and widely used in Brazil.

The World Energy Outlook projects biofuel use will increase rapidly over the next two decades as a result of rising oil prices and government support.

“The United States, Brazil and the European Union are expected to remain the world’s largest producers and consumers of biofuels,” the report states. “Advanced biofuels, including those from ligno-cellulosic feedstocks are assumed to enter the market around 2020.”

To reduce the cost of production, often higher than for imported oil, the report indicates strong government incentives will be needed to help biofuel become competitive.

Governmental agencies don’t seem to have as much trouble allocating funds for another eco-friendly travel option -- bus rapid transit -- as they do for rapid rail, Lovaas says. Dedicated lanes for buses, much like for trolleys or trains, allow for quicker travel. First popularized in Brazil, the concept is gaining momentum worldwide, he says.

With all the cutting-edge improvements, could the future of green transportation be now?

“Public policy even here in the U.S. is finally catching up and innovations in the private sector…could bend the fuel and emission curve.” And that just might help in the race against rising vehicle pollution.