Safe driving and received wisdom

[ArnieVXR]

I question how much advice on safe driving has been invented with good intention, as opposed to proven with unbiased research. For example, I was recently informed that I should keep two hands on the wheel and that to have only one leaves me open to callenged by the Law, as it's just not safe. This all seems very odd, as I guy I worked with only had one arm, but still held a driving license. The only modification to his car was the addition of a dolly to the steering wheel for low speed maneuvers. He had received no 'special' training prior to being issued with a license. None of this caused him to be unsafe. I drive a very fast dragster with one hand, which doesn't pose any problems either.

So who is right and is the 'two hands' advice merely received wisdom?

[ArnieVXR]

Guessing the car was heavily modified though.

[ArnieVXR]

Hi guys - my question was pitched more at understanding whether 'safe' is determined through empirical data or personal opinion.

The hands on wheel question is a great example, as the chap I worked with must be (as far as DVLA is concerned) safe enough in all situations to drive on the public highway. Taking that logic forward, two hands are therefore not necessary from a safety perspective in any scenario.