The driver is a woman who the trooper quickly confronts. He asks how much alcohol she's had, and is told "two drinks." But she's wobbly on her feet, and struggles with the basics in a field sobriety test. The breathalyzer comes back at .172 - more than twice the legal limit.
Handcuffs come next, but this is more than a single arrest. There's science behind this crime-fighting stop.
Trooper McDonald is part of the Washington State Patrol's Target Zero Teams initiated over the summer. It's a bold experiment to end drunk driving deaths in 20 years, and teams use science to map out DUI danger zones. McDonald has seen first-hand the damage they can do.
"You roll up on a crash that's block all lanes, people are bleeding, they are screaming for help," McDonald said.
The maps chart where the trouble spots are at. Wherever there's red, that's a DUI danger zone the State Patrol has assigned to its Target Zero Teams. Analysts are mapping out DUI danger zones in King, Pierce and Snohomish counties. Each yellow pinpoint marks a death from a drunk driving crash. The zones show where DUI incidents cluster.
Analysts like Marcia Marsh chart each crash, then overlays that with other data such as where 911 calls come in reporting suspected drunks. Using that, enforcement strategies are plotted, so troopers can be in position around these hot spots to intercept drunk drivers, before they crash and kill.
"We firmly believe that every drunk driver removed off the road is a potential life saved," Marsh said.
The maps confirm some suspicions and also reveal new trends. It's hard to steer clear of Downtown Seattle, where danger blankets the area. The zone saw 36 DUI deaths from 2005-09.
South Seattle is even worse, where drunk drivers killed 42 people in that time period - the most of any single zone.
Snohomish and Pierce counties also have risky corridors. Tacoma's deadliest times are weekdays after midnight. A total of 18 people lost their lives.
Puyallup's death toll is just as high, but crashes are more likely on the weekends, and many occur in the afternoons.
To the north, enforcement has tighter focal points because crashes tend to cluster in Snohomish County. The real trouble spots are in Mill Creek and Lynnwood, two cities that claim the county's highest rates for fatal DUIs.
Using this data, the 21-members of the Target Zero Teams have arrested 925 DUI suspects since July 1.
"We're not out here to pick on people," McDonald says. "We're out here to save lives."