Each year during the holiday season, the Ontario Provincial Police and local law enforcement agencies crack down on impaired driving throughout the province. The OPP's annual Festive RIDE campaign is underway, and drivers should be aware that this season the police have a particular interest in charging motorists not only with driving while impaired by alcohol, but also with driving while impaired by drugs.Compared to the number of impaired driving charges from last year, the number this year has been down significantly. However, the OPP reports that incidents of driving while impaired by drugs increased by 32 per cent. It is that kind of increase that gives police officers the incentive to send more drug recognition experts into the field during what is already a relatively busy season for impaired-driving charges.Usually, when a driver is accused of impairment by drugs, a drug recognition expert has documented the alleged impairment by administering standardized field sobriety tests. These tests are the "Horizontal Gaze Nystagmus" test, the "One-Legged Stand" test and the "Walk and Turn" test, all of which are meant to provide a way for assessing a driver's ability to do physical tasks with divided attention.However, standardized field sobriety tests are not always accurate indicators of impairment by drugs or alcohol, as the rate of error for each test is significant. Nonetheless, drivers throughout Ontario can expect the police to use field sobriety tests as the basis for impaired-driving charges this holiday season.If you have been stopped for allegedly driving while impaired, then you should speak with a lawyer as soon as possible about your defence options.