Police say Robert E. Daumer, 51, was driving the big rig in the northbound lanes at Edgemoor Road shortly before 1:00 p.m. when traffic suddenly slowed.
Daumer swerved to the left, police say, hit a guardrail then overcorrected and went to the right across all lanes.
The truck then went over that guardrail and came to rest.
Both Daumer and his passenger, 63-year-old Janis Chabak of Birdsboro, Pa. had to remain in the cab for about 90 minutes while rescuers stabilized the truck.
After being rescued, both Daumer and Chabak were taken to the hospital for treatment of their injuries.
Daumer was cited for following too close.
The northbound lanes of I-495 were completely shut down for more than two hours while the crash scene was cleared.