in a similar way. a roadside test to determine if the drug is in the system or not. then a further blood test at the station if needed. here is a little info...
When a police officer pulls you over, they must have reason to believe that you are driving while impaired by cannabis or other drugs. This includes if they saw you driving erratically or dangerously, or how you speak and interact with the police officer. On location, the police officer can ask you to complete a Standardized Field Sobriety Test (SFST) or provide an oral fluid sample (police are authorized to use oral fluid testing devices as part of the Bill C-46 legislation). If the driver fails these tests, a police officer can demand a Drug Recognition Evaluation (DRE) or blood sample for testing.
should note that the fluid test for thc is not very good as of yet. there are some groups fighting this as it is such a new thing.