TABLE A-1 (a): Energy Consumption as a Percent of
Total Energy Requirements for a Mid-size CarRolling resistance
Aerodynamic drag
Inertia (weight) force
TotalTractive energy
Accessory energy
Idle + braking consumption
Transmission + driveline lossPercentage of total tractive energy
City Highway Compositea
27.7 35.2 30.5
18.0 50.4 29.9
54.3 14.4 39.6
100 100 100Percentage of total fuel consumed
58.5 81.5 66.6
11.0 7.0 9.6
16.0 2.0 10.7
14.5 9.5 12.9a
Assumes that highway fuel economy = 1.5 X city fuel economy.
NOTE: Mid-size car of inertia weight=1588 kg, CD= 0.33, A = 2.1 m^2 ,CR=0.011, 3L OHV V-6,
power steering, four-speed automatic transmission with lockup, air conditioning.
SOURCE: Derived from G. Sovran and M. Bohn, “Formulae for the Tractive Energy Requirements of
Vehicles Driving the EPA Schedules,” SAE paper 810184, 1981.