"What makes cities in India and China so frustrating to drive in - heavy traffic, aggressive driving style, few freeways - makes them ideal for saving fuel with hybrid vehicles," according to researchers at the US Department of Energy's Lawrence Berkeley National Laboratory (Berkeley Lab).
In a pair of studies using real-world driving conditions, researchers found that hybrid cars are significantly more fuel-efficient in India and China than they are in the US.
These findings could have an important impact in countries that are on the brink of experiencing an explosion in the sales of personal vehicles, researchers said.
"Currently greenhouse gas emissions from the transportation sector in India and China are a smaller piece of the pie compared with other sectors," said lead researcher Anand Gopal.
"But vehicle ownership is going to skyrocket in these countries. That is why we decided to focus on this area. Hybrid and electric vehicles can significantly reduce carbon emissions and other pollutants," said Gopal.
Hybrids in India are also more fuel-efficient than they are officially rated for, researchers said.
"With the official fuel economy test procedure currently used in India, fuel savings for hybrids are fairly grossly underestimated, showing only a 29 per cent savings over conventional vehicles," Gopal said.
"The test cycle is not representative of driving conditions in India, so that's sending the wrong signal to the consumer," said Gopal.
Gopal, working with Berkeley Lab scientists Samveg Saxena and Amol Phadke, used a power-train simulation model called Autonomie to create a hypothetical hybridised version of the top-selling conventional car in each country.
Researchers simulated drive cycles in two Indian cities (New Delhi and Pune) taken from published studies and also used the Modified Indian Drive Cycle, the test for the official fuel economy rating.
In China they simulated drive cycles in 11 cities and with three types of hybrid power-trains (start-stop, parallel and power-split).
In both cases they compared it to drive cycles used for US fuel efficiency ratings, which include about 55 per cent city driving and 45 per cent highway driving.
They found that driving a hybrid would achieve fuel savings of about 47 to 48 per cent over a conventional car in India and about 53 to 55 per cent in China.
In the US, hybrids are rated to produce a fuel savings of about 40 per cent over their conventional counterparts.
Currently hybrid and electric vehicles have a tiny share of the market in India and China and are seen as a higher-end product, researchers said.
The results appear in the International Journal of Powertrains.