Your Prius Was Made For Beijing Traffic

It turns out that hybrid vehicles’ fuel efficiency varies from country to country, due in part to “national driving styles”:

When the computer generated vehicles were “driven” according to the real world driving data, the hybrids generated fuel savings of 48 percent in India and up to 55 percent in China, compared with around 40 percent in the US. Why the discrepancy? At low speeds, such as found in many cities, the internal combustion engine is inefficient, and so in the hybrids the electric motor took over. Energy recovered through regenerative breaking – when the electric motor is allowed to run backwards as a generator when the car is slowing – was, as expected, the main reason why they hybrids were much more efficient.

The second most important factor surprised the researchers. “We forgot about the aggressiveness of the driving styles,” says [researcher Anand] Gopal. “Dense traffic and aggressive driving styles favor hybrids.” In India and China, driving involves a lot of accelerating and braking – which can both be done more efficiently with an electric drive train versus a petrol engine. Although a major road in Los Angeles or London may be a pain to get through at rush hour, it does not require the levels of hard, emergency, braking required in New Delhi, Gopal says. Drives that include more time in traffic jams and fewer motorways also generated greater benefits from hybrids.