Consider the following types of vehicles: [Defence]

I. Full battery electric vehicles

II. Hydrogen fuel cell vehicles

III. Fuel cell-electric hybrid vehicles

How many of the above are considered as alternative powertrain vehicles?

The correct answer is All the three.

Alternative powertrain vehicles refer to vehicles that run on non-traditional power sources or propulsion technologies, diverging from the standard internal combustion engine (ICE) that relies solely on gasoline or diesel. These technologies aim to reduce greenhouse gas emissions and dependency on fossil fuels.

Let us analyze each of the given vehicle types:
1. Full battery electric vehicles (BEVs): These vehicles run entirely on electricity stored in a battery pack. They do not have an internal combustion engine and produce zero tailpipe emissions, making them a primary type of alternative powertrain vehicle.
2. Hydrogen fuel cell vehicles (FCEVs): These vehicles use hydrogen gas to run an electric motor. The hydrogen is reacted with oxygen in a fuel cell to generate electricity, with water vapor being the only byproduct. This represents a distinct alternative to conventional fossil-fuel-based drivetrains.
3. Fuel cell-electric hybrid vehicles (FCEHVs): These combine a fuel cell system with an electric battery storage system to improve efficiency, range, and power delivery. Since both power sources (fuel cells and electricity) deviate from standard internal combustion systems, they are also classified under alternative powertrains.

Therefore, all three of the listed options (I, II, and III) are considered alternative powertrain vehicles.