A common habit while driving, is to cross your arms when turning the steering wheel. It seems a harmless thing to do, and people often wonder why qualified driving instructors and examiners insist on the “feeding” or “push-pull” method. (Note: a driving examiner won’t normaly fail a pupil for crossing their arms, providing it does not cause a problem in their driving)
But there are a couple of good reasons to avoid crossing your arms. One, is that if you are turning the wheel while the car is moving at speed, and you have to swerve away from an unexpected obstacle such as a pot hole or debris on the road while your arms are crossed, you may actually obstruct yourself while trying to change direction.
Another thing to consider in the majority of modern cars, is that while your arms are crossed, they are between you and your air bag. If you are unfortunate enough to have a bump while your arms are crossed (and as hinted above because your arms are crossed!) then you have the airbag to worry about.
Remember, airbags are designed to inflate rapidly on impact, and expand at a rate up to 200 mph. If your arms are in the way your own hands will be flying towards your head at the same rate! (ouch!)