Final answer:
The fuel efficiency in hybrid vehicles primarily increases due to the integration of an electric motor with a gasoline engine, regenerative braking, and efficient transmissions. Other factors include advanced engine technologies and improved emissions standards.
Step-by-step explanation:
Hybrid vehicles are designed to improve fuel efficiency and reduce emissions compared to conventional internal combustion engine vehicles. The increase in fuel efficiency in hybrid vehicles comes largely from the combination of an electric motor with a gasoline engine, which allows the vehicle to operate more efficiently by taking advantage of technologies such as regenerative braking and electric drive. Regenerative braking recovers energy that would otherwise be lost during deceleration and stores it in the battery, while the electric motor's ability to deliver energy more efficiently than a gasoline engine contributes significantly to overall fuel economy.
Furthermore, hybrid vehicle technology often includes advanced transmission technologies such as dual clutch transmissions (DCTs) and continuously variable transmissions (CVTs), which help improve fuel economy and reduce CO₂ emissions. Engine technologies such as variable valve timing, multi-valve engines, turbocharging, and gasoline direct injection also contribute to the enhanced efficiency of these hybrids. Lastly, the use of catalysts and improved fuel standards works to reduce the vehicle's environmental impact by lowering harmful emissions.