A Metrobus hit a sedan on westbound Interstate 66 near the Dulles Toll Road, sending four people to the hospital with injuries that were not life-threatening, according to authorities.
The Virginia State Police were called to the scene shortly after 4 p.m., according to police spokeswoman Corinne Geller.
After the crash, the bus came to rest against the guardrail off of the road. There were between 30 and 35 people on the bus when the crash occurred.
Two riders on the bus as well as the drivers of both vehicles were taken to Reston Hospital in ambulances.
The bus involved was on the 5A route to Dulles International Airport, said Metro spokesman Dan Stessel. The bus operator reports that a car merging onto I-66 swerved into the bus and then into a concrete wall, Stessel said.
This crash caused major delays on I-66, with lane closures and severe backups snarling traffic just as the evening commute got underway.
Another Metrobus arrived shortly after 5 p.m. to pick up the stranded riders.