It is generally accepted that driving with a vehicle’s windows down is more fuel efficient than running the air conditioner when travelling at low speeds. However, not all passengers may feel the same comfort levels.  Convective heat transfer coefficients for each passenger in a vehicle were estimated for different window configurations on a simplified shape of a large Australian car travelling a 60km/h. 

Some of the modelling results were counter intuative.  Rear passengers were found to be subject to greater convective cooling even though only the front windows were open. 

 More details of this case study can be found here.