Strength for Control Operation:
Strength is one type of human performance limiting factor and concerns the application of force in the operation of controls and in other physical tasks. Often, limitation of strength imposes a one-way constraint and it is sufficient to determine the level of force that is acceptable for a weak limiting user.

The capabilities of the human body are considered to make the operational components of the vehicle while driving. For example, force is required for the ease of operation of clutch, steering, opening and closing of doors etc.

Actuating force limits for some important tractor controls for Indian male agricultural workers (CIAE, Bhopal, 2009) are given below:

Brake Pedal:
- 5th p Rt leg strength (male)=261 N.
- Maximum actuating force for break operation should be less than 260 N.

Clutch Pedal:
- 5th p Lt leg strength (male)=247 N.
- Frequently operated compared to the brake pedal.
- 50% of 5th p Lt leg strength (male)= 123.5 N.
- Maximum actuating force for Clutch operation should be less than 124 N.

Accelerator Pedal:
- 5th p Rt foot strength (male)=163 N.
- Continuously operated, 30% of 5th p Rt foot strength (male)=49 N (upper limit).
- Maximum actuating force for accelerator operation should be less than 49 N.
- Weight of leg = 9%= .09 of body wt., part of this wt. is supported by heel.
- Lower limit of force exertion for accelerator= 54.7kg x9.81x.09x0.5=24N.

Steering Wheel:
- 5th p torque strength with both hands, sitting (male)=36 Nm (force 171 N with lever arm of    0.21 m).
- Frequently operated, 30% of 5th p = 51 N.
- Maximum actuating force for steering wheel operation should be less than 51 N.

Gear Selection/ Speed Selection Lever:
- 5th p Rt hand push strength = 49 N, limiting force for operation.
- Maximum actuating force for gear operation should be less than 49 N.