Hybrid vehicles use a combination of conventional and electric-powered engines to enhance fuel efficiency and reduce carbon emissions.
There are many different types of hybrid engine designs, but all tend to combine an internal combustion engine and an electric motor that can either work together or separately to propel the vehicle.
The electric motor, which draws on a battery that recharges itself by harvesting lost power when the vehicle brakes, tends to dominate at lower speeds resulting in significantly improved fuel efficiency, particularly in urban traffic conditions.
Next generation Series Hybrids, use only an electric motor powered by an internal combustion engine to provide propulsion - a move which advocates claim will deliver further improvements in fuel efficiency.
Toyota dominates the market for hybrid vehicles with its iconic Prius, but a raft of high profile manufacturers including Honda, Lexus and BMW have subsequently released hybrid versions of their vehicles into what is becoming an increasingly competitive market.
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