CSA B335-04,

4.9.3.7
Where steering must be accomplished with one hand using a steering handwheel, a steering ****(s) or an equivalent shall be used to promote safe and effective operation. the steering handwheel and **** configuration shall be of a design that will minimize the hazard from a spinning handwheel due to a driving surface reaction feedback, or a steering mechanism shall be of a type that prevents driving surface reactions from causing the steering handwheel to spin. The steering wheel ****(s) shall be within the periphery of the steering handwheel.

4.9.3.8
Where steering can be accomplished by either hand, and the steering mechanism is of a type that prevents driving surface reactions from causing the handwheel to spin (power steering or equivalent), steering knobs may be used. When used, steering knobs shall be of a type that can be engaged by the operator's hand from the top, and shall be within the periphery of the steering handwheel.

That should answer your question regarding the Candian Standards Assciation guidelines, being from Quebec 'n all. However, I do agree with joseph h that 2 hands are better than one. In certain circumstances, based upon my experiences, there are certain trucks, especially the older ones, where the **** does make steering much easier, especially when the students are operating the sit-down counterbalance forklifts, through the obstacle courses. The heaviness of the steering wheel along with the wheel's diameter, make turning the truck rather awkward.

Take it from there.....