Quick Summary of this Physics Note:

• Electric Vehicles (EV): High efficiency (~90%), zero roadside emissions, but limited by battery range and charging time.

• Hybrid Vehicles (HEV): Achieve efficiency through Idle Stop, smaller engines, and Regenerative Braking (converting KE to electrical energy).

• Engine Comparison: Diesel engines are more efficient (35-40%) than petrol (~25%) but emit more particulates (soot). LPG is used in HK taxis for cleaner air.

• Mass Transport: Rail is the most efficient due to low rolling resistance (steel on steel) and high passenger capacity. MagLev trains eliminate friction entirely.