Perhaps the most common of bad steering habits, the classic ‘one-armed bandit’ pose is rarely through choice. In fact, this grip with just the one hand on top of the steering wheel is usually a result of sitting too far from the wheel. Over time, the arm and shoulder muscles fatigue, and short of letting go of the wheel altogether, this is one of the few remaining comfortable options. If you can identify with this pose, you may find the following of interest.
If you are happy with the general seating position and distance from the pedals, the steering wheel can be moved to suit you. Most cars have both height (up/down) and reach (in/out) adjustment via a drop-down lever or electric control. A good position will allow you a pose with a near-90 degree bend at the elbow. This will give enough space to steer effectively but reduce that muscle fatigue. Improved control via a two-handed grip can now be easily achieved.