Detention of persons affected by alcohol or a drug

A person required to provide a specimen of blood or urine may thereafter be detained at the police station until it appears to a police officer that, were that person then driving or attempting to drive a motor vehicle on a road, he would not be committing an offence under section 74 or section 75; but– (a) a person shall not be detained in pursuance to this section if it appears to a police officer that there is no likelihood of his driving or attempting to drive whilst his ability to drive properly is impaired or whilst the proportion of alcohol in his blood or urine exceeds the prescribed limit; and (b) a police officer shall consult a registered medical practitioner on any question arising under this section whether a person’s ability to drive properly is or might be impaired through Motor Vehicles and Road Traffic [CAP. 230 57 drugs and shall act on the medical practitioner’s advice.