Cost of Transport

The energy used to move a unit of weight a unit of distance — a measure of how efficient walking or running is.

Cost of transport is a dimensionless measure of locomotion efficiency: CoT = E/(mgd) = P/(mgv), where E is energy consumed, m is mass, g is gravitational acceleration, d is distance traveled, P is power, and v is speed. Lower is more efficient, and because body weight and distance cancel out, the number can be compared across animals, vehicles, and robots on equal footing. Collins, Ruina, Tedrake, and Wisse reported in a 2005 Science paper that the Cornell biped, built around passive-dynamic walking, achieved a cost of transport of about 0.2 — comparable to human walking — while Honda's ASIMO was around 3.2. For legged and humanoid robots this number directly determines battery range. When comparing figures, it matters whether E is measured as motor mechanical work, total battery electrical energy, or human metabolic energy — these give very different numbers for the same task.

ExampleA commonly cited example: a 70 kg person walking at 1 m/s has a metabolic power of about 231 W, giving CoT ≈ 231/(70×9.8×1) ≈ 0.34.

Also called

CoT, Specific Cost of Transport, Specific Resistance

Related

Passive Dynamic Walking · Bipedal Locomotion · Legged Locomotion · Gait · Battery Runtime

Sources

Wikipedia: Cost of transport
Wikipedia: Passive dynamics（Cornell biped 0.20、ASIMO 3.23）