WALTHAM, MA - State Police on May 4th reported a tractor-trailer accident on I-95 South at the Route 20 exit. Waltham dispatched Engine 2, Rescue 1 and Medic 1. Units found a tractor-trailer with heavy damage in the left lane, a box truck turned sideways, a car into the rear of the tractor-trailer, and a car up the highway. Firefighters tended to three people who were transported to Newton Wellesley Hospital, and one person who was transported to Beth Israel Hospital in Boston. Traffic was backed up five miles southbound for about two hours during the incident. State Police were investigating.