ZE Buses
Zero emission buses (ZE buses) are buses with no tailpipe emissions.
Types of ZE buses: Battery electric vehicle (BEV), fuel cell electric vehicle (FCEV), plug-in hybrid electric vehicle (PHEV).

Battery electric vehicle
Battery electric vehicle (BEV) uses electricity stored in rechargeable battery packs, with no secondary source of propulsion. BEVs use electric motors instead of internal combustion engines (ICEs) for propulsion.

Fuel cell electric vehicle
Fuel cell electric vehicle (FCEV) uses electricity from a fuel cell to power an electric motor, instead of drawing electricity from a battery. The fuel cell is usually powered by hydrogen to generate electricity.

Plug-in hybrid electric vehicle
Plug-in hybrid electric vehicle (PHEV) uses both electric motors and internal combustion engines.
Source: U.S. Department of Energy, Hydrogen London, European Federation for Transport and Environment