A dangerous highway drama occurred Saturday south of Washington in Virginia amid the river of cars flowing along one of the region’s major arteries, Interstate 95. It highlighted the unexpected perils of highway travel.

It involved, according to the Virginia State Police, two motorists behaving aggressively. It drew in a state trooper and a driver whom the trooper had stopped.

It ended with four people being treated at a hospital, the trooper and the driver he had stopped among them. None of the injuries was described as life-threatening.

According to state police, a 2012 Nissan SUV and a 2004 Ford pickup were “driving aggressively towards one another” about 8:15 a.m. while southbound. At the 134 mile marker in Stafford County, while changing lanes, the police said, the two vehicles “made contact.”

The Nissan spun off the right side of the highway. Trooper K.J. Zalasar, 30, was in a patrol car on the right hand shoulder, where he had stopped a car.

The Nissan left the road at the very spot where Zalasar was sitting in his patrol car. His car was struck, police said, and was forced into the car he had stopped.

The driver of the Nissan, Alexandra M. Seaman, 24, of Woodbridge, Va., was injured, along with her passenger, police said. The Ford’s driver, Christopher P. Johnson, 35, of Powhatan, Va., was unhurt, they said. Police said Seaman and Johnson were both charged with reckless driving.