● Driving efficiency heavily depends on the resistance forces. Total resistance in auto drive with constant speed consists of rolling resistance,
which is proportional to vehicle mass and air resistance, which is proportional to square of velocity. Acceleration (Inertial) resistance
and grade resistance does not depend on a level road and at constant speed. (TR=RR+AR, Frr α Mg, Far α V2)
● Efficiency of 2-wheel vehicle decreases faster along with the increase velocity, because air resistance increases proportionally in spite of relatively small rolling resistance of its lighter mass.
With higher air resistance coefficient of 0.2 compared to 0.3 of 4-wheel vehicle, the increase in velocity of motorcycle sensitively drops efficiency. In a passenger car, the rolling resistance is double of air resistance until velocity of 80km/h , which results in low decrease of efficiency.