Carpooling decreases the amount of cars used to travel to a place.
Arrange carpools to conserve fuel.
Decreasing the amount of cars used to travel conserves fuel.
Decreasing what during travel likely conserves fuel?
  the energy of the car
  air mass over Earth's surface
  the amount of cars used
  the size of the wheels
  the amount of water used
  kinetic energy
  preventing heat transfer
  energy usage