The Department shall not issue a driver's license to any person when, in the opinion of the Department, such person is suffering from an impairment that will prevent his exercising reasonable and ordinary control over a motor vehicle while driving it on the highways, nor shall a license be issued to any person who is unable to understand highway warning or direction signs.
The term "impairment" shall not mean inability of a person to hear or to speak, or both, when he has good vision and can satisfactorily demonstrate his ability to drive a motor vehicle and has sufficient knowledge of traffic rules and regulations.