Power-defined Climbing Ability
Using the traction force diagram, it is possible to determine in a simple way, the excess traction force FX,ex as a difference of the demand force Fdem and the available traction force FX. The resulting characteristic of excess traction force over the driving speed is shown in the figure.
In order to drive on an upward gradient, the climbing resistance Fgr has to be overcome (see Chapter 2.3). The following is applicable for the climbing resistance:

Eq. 3-8

where: αgr= angle of gradient
Since driving at a constant velocity is a prerequisite for the determination of the power-defined climbing ability, the entire excess traction force is available by comparing supply and demand at a constant velocity drive in the plane in order to overcome the climbing resistance.
At a prescribed speed and gear level, the maximum climbing ability defined by power results from the following relation:

Eq. 3-9

Thus the power-defined climbing ability is proportional to the excess traction force (as seen in the figure).