Brown Timothy, Kruse Cole, Schmitt Rose, Gaffney Gary, Milavetz Gary
University of Iowa Driving Safety Research Institute, Iowa City, Iowa.
College of Liberal Arts and Sciences, University of Iowa, Iowa City, Iowa.
Traffic Inj Prev. 2025;26(1):10-19. doi: 10.1080/15389588.2024.2393215. Epub 2024 Sep 20.
The objectives of this study were 1) to identify the effects cannabis has on driving performance and individual motor practices when on the freeway compared to placebo and 2) to bring context to the effects of cannabis on driving by comparing effect sizes to those of alcohol.
Data for analysis was collected from a study of fifty-three participants with a history of tetrahydrocannabinol (THC) cannabis use who completed three visits in randomized order (placebo (0% THC), 6.18% THC, and 10.5% THC). Data for the alcohol analysis was from a subset of eighteen of these participants with a history of recent alcohol use that completed a fourth alcohol visit that targeted a .05 g/210L breath alcohol content (BrAC) during the drive. Comparisons were made using an analysis of variance approach with the SAS General Linear Models Procedure. Cohen's effect sizes were calculated for the cannabis and alcohol conditions relative to placebo for both the full sample and alcohol subset.
Standard deviation of lane position (SDLP) for cannabis significantly increased compared to placebo and the effect size was comparable to that of alcohol at .05 BrAC. Lane departures for cannabis significantly increased relative to placebo as did the time out of the lane. Cannabis use resulted in an increased amount of time at 10% or more below the speed limit for the 6.18% THC condition. Relative to alcohol, cannabis produced more time at slower speeds and less time at speeds more than 10% above the speed limit.
Multiple factors of lateral and longitudinal vehicle control on the freeway showed statistical significance. Drivers under the influence of cannabis exhibited higher rates of driving errors but also showed more cautious behaviors such as generally lower speeds on the freeway. Compared with alcohol, effect sizes varied. For longitudinal control, there were larger effect sizes for alcohol with speed effects in opposite directions, but relatively equivalent effect sizes for lateral control and driving errors associated with lane keeping.
本研究的目的是：1）确定与安慰剂相比，大麻对在高速公路上驾驶性能和个体运动行为的影响；2）通过将大麻影响的效应大小与酒精的效应大小进行比较，来了解大麻对驾驶的影响。
分析数据来自一项对53名有四氢大麻酚（THC）使用史的参与者的研究，他们按随机顺序完成了三次访视（安慰剂（0% THC）、6.18% THC和10.5% THC）。酒精分析的数据来自其中18名近期有饮酒史的参与者的子集，他们完成了第四次酒精访视，目标是在驾驶期间达到0.05 g/210L的呼气酒精含量（BrAC）。使用SAS通用线性模型程序采用方差分析方法进行比较。针对大麻和酒精条件相对于安慰剂，计算了全样本和酒精子集的科恩效应大小。
与安慰剂相比，大麻组的车道位置标准差（SDLP）显著增加，效应大小与0.05 BrAC时的酒精效应大小相当。与安慰剂相比，大麻组的车道偏离和驶出车道的时间显著增加。在6.18% THC条件下，使用大麻导致低于限速10%或更多的时间增加。相对于酒精，大麻导致在较慢速度下的时间更多，而在高于限速10%以上的速度下的时间更少。
高速公路上车辆横向和纵向控制的多个因素具有统计学意义。受大麻影响的驾驶员表现出更高的驾驶错误率，但也表现出更谨慎的行为，如在高速公路上总体速度较低。与酒精相比，效应大小有所不同。对于纵向控制，酒精的效应大小更大，速度效应方向相反，但对于横向控制和与车道保持相关的驾驶错误，效应大小相对相当。
