Driving simulator studies of marijuana alone and in combination with alcohol

The relationship between performance on the standardised field sobriety tests, driving performance and the level of Δ9-tetrahydrocannabinol (THC) in blood

“…These findings are consistent with previous research that has revealed that THC impairs car control [3], increases the number of obstacles hit on a driving course [4,5], increases the standard deviation of the lateral position of a vehicle [5,6], impairs tracking ability [6] and increases the number of sideways movements of a vehicle, as well as the percentage of time spent out of a lane [5,7].…”

“…By way of contrast, the odds ratio of drivers who presented with a blood alcohol concentration (BAC) of between 10 and 15 was 3.7 and the odds ratio of drivers in whom neither drugs nor alcohol were detected was 1.0 [2]. www The consumption of THC has been shown to lead to impaired car control [3], increase the number of obstacles hit on a driving course [4,5], increase the standard deviation of the lateral position of a vehicle [5,6], impair tracking ability [6] and increase the number of sideways movements of a vehicle as well as the percentage of time spent out of a lane [6,7].…”

Separate and combined effects of marijuana and alcohol on mood, equilibrium and simulated driving

“…In on-road studies that quantified lane position and speed, THC-intoxicated drivers maintained a longer distance from the car in front of them and drove slower through obstacle courses (Robbe and O'Hanlon 1993). Marijuana has slowed reaction time on tasks during simulated driving that are of secondary importance to vehicle operation (Moskowitz et al 1976;Smiley et al 1981), suggesting that distraction may be a key factor in marijuana-related collisions. However, effects of THC on direct emergency responding appear to be dependent on whether subjects have some warning or other knowledge of when that response is needed.…”

Sex Differences in the Effects of Marijuana on Simulated Driving Performance

“…More cautious driving behaviors were found in several studies (Lamers & Ramaekers 2001; Stein et al 1983; Ellingstad, McFarling & Struckman 1973; Rafaelsen, Bech & Rafaelsen 1973; Dott 1972), while an increased reaction time for stopping was the most common finding (Liguori, Gatto & Robinson 1998; Rafaelsen, Bech & Rafaelsen 1973). Moskowitz (Ziedman and Sharma 1976) also found slowed reaction times for a visual choice-reaction time task administered while driving and Smiley, Moskowitz and Zeidman (1981) found increased variability in velocity and lateral position while following curves and while controlling the car in gusts of wind with a high dose of marijuana (200 mcg/kg THC) but not with a lower dose (100 mcg/kg THC). They also found an increase in variability of headway and lateral position while following other cars.…”