Recent studies of the incidence of illicit drugs have increased to 18% of road accident fatalities in the UK in recent research and while the drugs did not necessarily cause the accidents the increase is cause for concern. Cannabis comprised two-thirds of total drug use. An increase in multiple drug use had also occurred. Drug users were no more likely to be over the drink drive limit than non drug users. In 1999 only 2000 samples were submitted by police for suspected drug driving compared with 800,000 roadside breath tests, implying that drug-impaired drivers go undetected by police. Trials of two drug screening devices, Drugwipe (using perspiration) and Cozart (using saliva), were conducted. The devices were found acceptable. Drug recognition training for police was also undertaken. Of those drivers who failed a field impairment test, 92% proved positive for drugs. Other methods of assessing drug impairment are being developed and these are discussed. It is suggested that adopting a zero tolerance option to drug driving would simplify testing and law enforcement. A study of the effects of cannabis on driving was conducted using the TRL driving simulator. Cannabis use reduced driving speeds by about 5mph, caused more cautious behaviour but did not compensate for the loss of capability in some psychomotor skills including tracking ability. Increased dose worsened performance. General medical examination and standardised impairment testing of the subjects by police surgeons were effective in determining impairment.
Abstract