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NIDA. (2015, October 5). Read This If You Know People Who Smoke Weed and Then Drive (Part 1). Retrieved from

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The NIDA Blog Team
October 5 2015
Photo of a driving simulator

Everybody knows how dangerous it is to drink and drive. (A refresher: Drunk driving kills over 10,000 people every year.) That’s why states established a blood alcohol concentration limit for drivers; if you’re pulled over and the alcohol in your breath is above that limit (.08 percent), you’re considered to be Driving Under the Influence (DUI) or Driving While Impaired (DWI).

Now, with more states in the U.S. legalizing marijuana for medical and/or recreational use, there’s an increasing need to know the potential risks of “drugged driving.”

To find out, NIDA joined forces with the Office of National Drug Control Policy (ONDCP), and the National Highway Traffic Safety Administration (NHTSA) for a three-year study on how inhaling marijuana with and without drinking alcohol affects the way people drive. In this two-part series we’ll show you just how they did it, and what they found out!

Driving without actually driving

Researchers can now measure driving performance safely, by using the University of Iowa's National Advanced Driving Simulator (NADS), which features state-of-the-art technology to mimic the driving experience in a very convincing way. Other driving simulators are more like video games, but NADS puts you in a real car, surrounded by a 360-degree virtual environment. It also measures tiny details, like where your eyes are looking when you face certain driving obstacles, such as pedestrians and oncoming traffic.

NADS was developed by NHTSA to enable research that aims to reduce driving accidents, injuries, and deaths by studying how people drive in certain situations, and the ways that certain driving conditions can contribute to safer driving. For instance, what are the safest designs for intersections, entrances and exits, highway signs, and so on?

It’s a lot less expensive—and yes, a lot safer—to try out different options for roads, signs, etc., without having to actually build them. And a bonus for NIDA’s research: the simulator is just as effective at measuring how people drive under the influence of various drugs.

Driving Simulator 101: better than Blu-Ray

The main NADS set-up is a large dome, mounted on a rig that slides and tilts in all directions to give the “driver” sensations of motion. Engineers can install entire cars, and the cabs of trucks and buses, inside the dome. Every vehicle used in the NADS has the exact same interior instruments (dashboard, steering wheel, lighting, etc.) that its real make and model has.

The motion system creates such a realistic driving experience that drivers feel steering, acceleration, and braking just as they would when driving a real vehicle. The latest visual and audio technology can create all kinds of driving settings and situations: from parking lots to city streets to gravel roads, from oncoming traffic to cars that swerve into your lane as they pass.

Can you juggle and drive?

NADS shows a lot more than whether a driver could get into an accident. When you’re driving, it may feel like all you’re doing is watching the road, but you’re actually paying attention to dozens of different things at the same time. It’s kind of like mental juggling.

For instance, you’re monitoring whether you’re staying in the lane; using peripheral vision to note what’s in your immediate environment; observing what the car in front of you is doing, your distance from it, and what’s behind you in the rearview mirror; keeping tabs on your speed; and a lot more. Hopefully you’re able to keep doing all of that even when momentarily distracted, as when you glance at a GPS.

NADS is outfitted with interior cameras and other devices that constantly gauge how well a driver handles all these tasks in different driving scenarios. It provides the most thorough data possible on someone’s minute-to-minute driving performance.

So, back to the NIDA/ONDCP/NHTSA study using NADS: we’ll look at the first set of results in our next post: “Read This If You Know People Who Smoke Weed and Then Drive (Part 2).”