"driving under the influence"
Any drug that changes your mood, or the way you see and feel, will affect the way you drive. This is not only true for illegal drugs. There are prescription drugs and some over-the-counter drugs that can also impair your driving ability.
Remember, fatigue and stress will also affect your ability to drive.
You will be subject to a roadside test if the officer has reason to believe you are under the influence, you will face the charge of Impaired and driving under the influence should you be deemed impaired by the testing officer.