pjpekala

As cannabis is legalized across the country, an argument against it's legalization is the lack of ability to determine impairment like there is with alcohol. What is the NTSB doing to ensure that law enforcement has an accurate way to determine the impairment of drivers under the influence of marijuana, as the active compounds can linger in the body for some time after use and does not accurately reflect level of impairment?

Has the NTSB seen a rise or fall in cannabis related traffic accidents in states that have legalized? What about the proportion of alcohol related to other drug related accidents or polysubstance accidents in these states vs non legal states?