Is this a step too far?
Drug testing is a challenging issue for both the employers and employees. It can be a sensitive issue in the workplace.
When employers are formulating drug policies it is important to note that if the word impairment is included, then there has to be a way for this to be measured.
I would always advise that if you intend to run any kind of workplace testing procedures that you find a way to explain to employees exactly what that means, and provide additional information about the actual effects of drug and alcohol use.