According to Reefer Sanity by Kevin Sabet...
- Marijuana use significantly increases the risk of a car crash.
- Marijuana levels are difficult to interpret, unlike alcohol, where we do have reliable bio markers to help determine whether a person was driving while intoxicated.
- A test for marijuana would test positive even if the user smoked days before and was not impaired at the time of the test.
- "It is extremely difficult to establish a blood concentration level that correlates to impairment levels for marijuana" (p. 101)
- "Marijuana impairs a driver's sense of spatial location and sense of time and speed, whereas alcohol impairs speed and reaction time" (p. 101)