A method of operating a vehicle, comprising: receiving ambient air information; receiving size, distance and relative velocity information about a vehicle in proximity to the vehicle; receiving road surface properties information; receiving wind velocity and direction information; computing an air density ratio factor using the ambient air information; computing an aerodynamic drag ratio factor using the size, distance and relative velocity information; computing a rolling resistance ratio factor using the information road surface properties information; computing effective velocity of the vehicle using the wind velocity and direction information; combining at least one of the air density ratio factor, the aerodynamic drag ratio factor and the rolling resistance ratio factor with vehicle loss coefficients to determining new vehicle loss coefficients; computing an energy loss or power loss of the vehicle using the new vehicle loss coefficients and the effective velocity of the vehicle; and controlling the vehicle to improve fuel economy.