Section 5A(1) and (2) of the Road Traffic Act 1988 makes it an offence for a person to drive, attempt to drive, or be in charge of a motor vehicle on a road or other public place with a specified controlled drug in the body, if the proportion of the drug in that person's blood or urine exceeds the specified limit for that drug. These Regulations specify amphetamine as a controlled drug for this purpose as well as the specified limit for amphetamine expressed as a concentration in blood.