The attacks happened at the Broad Street and Duke Street overpasses in the last week. Police believe someone is using rocks from a construction site as a dangerous weapon.
Sunday night, rocks thrown off an overpass above I-85 damaged two vehicles and injured one person.
A Triad woman was injured when a rock crashed through her window and cut her hand. She was a passenger in a car being driven by her husband.
None of the other victims was seriously injured.
The first two attacks in the last week happened on Broad Street, on the same night at the same time. The last two happened on Duke Street, again on the same night at the same time.
Police say the suspects are probably juveniles playing a prank.
"If I had to give a professional opinion, I'd say it's kids being stupid," said Durham police Capt. C.D. Clark. "But it can resuilt in a death, and there's nothing stupid about that. That's serious."
Rocks also were thrown through the windows of a piece of construction equipment parked nearby in the 1700 block of N. Buchanan Blvd.
It is not known if the same people are responsible for all the incidents.
Witnesses reported seeing juveniles running from the overpass toward Ruby Street after two of the incidents.
Anyone with information about the incidents is asked to call CrimeStoppers at
or District 2 police substation at
CrimeStoppers pays cash rewards for information leading to arrests in felony cases.
This is not the first rash of rock-throwing incidents on Durham overpasses. In 1999, a woman was killed when a boulder was dropped onto her car from an overpass.
Sunday's incidents brought back memories of a 1999 incident in Cumberland County in which a boy from Canada suffered permanent brain damage.