Natural gas is very much in the public consciousness right now, if not for all the best reasons.
Seen as a cleaner, more energy-independent fuel than fossil fuel oil, it nevertheless has its detractors, largely concerning the 'fracking' process through which it is extracted from the ground.
But its benefits mean that it has plenty of potential as an automotive alternative fuel. In some countries it already is--and a chart by NGV Global shows just where natural gas vehicles are most popular.
Unsurprisingly, that isn't in the U.S.
Natural gas vehicles as a percentage of total vehicles (NGV Global)
Based on IRF 2008 data and UNECE 2011 data--so it's not completely current, but it's recent at least--just 0.05 percent of cars sold in the U.S. run on natural gas.
In numeric terms, that equates to around 127,000 of the quarter-billion vehicles on U.S. roads.
In contrast is Pakistan, situated to the north west of India. Of the country's 4.5 million vehicles, 2.9 million--just under 65 percent--are powered by natural gas.
The country produces natural gas at a high rate and much of Pakistan's electricity is generated using natural gas--though heavy industrial use means reserves may last only another twenty years.
Highest of all--though home to just 315,000 vehicles, is Armenia. Located between the Caspian and Black seas, over 77 percent of the country's vehicles are powered by natural gas. Bolivia, Iran, Argentina, Bangladesh and Uzbekistan all follow.
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Of those, Iran has the highest number of natural gas vehicles of any nation--three million, or a fifth of the nation's vehicles. That may come as no surprise--the oil-rich nation is also gas-rich, with just under 16 percent of the world's natural gas reserves.
The majority of nations worldwide have natural gas vehicle proportions of less than one percent, so America shouldn't feel too left-out.
While the country's natural gas reserves are high, using the gas as fuel has so far been of low-priority--like any other alternative, the availability of cheap gasoline has meant little demand for alternatives.
There are still relatively few natural gas vehicles for sale in the U.S. too, and most of those are commercial vehicles. Throw in a shortage of places to actually fuel up, and the low demand is unsurprising.
The fuel has its advocates, and there have been recent moves to introduce a diesel-equivalent measurement for natural gas to promote its use.
But don't expect natural gas vehicle sales to shoot up any time soon. The availability of diesels, hybrids and plug-in vehicles already gives American consumers plenty of options when it comes to reducing fossil fuel use and cutting fuel bills.