Four people escaped serious injury late Tuesday in a two-car crash that heavily damaged both vehicles on the Merritt Parkway, between Exits 42 and 44 northbound in Westport.

One of the vehicles, a BMW, rolled down an embankment of the highway and the other, a Ford Escape, was still in the left lane when Westport firefighters arrived on the scene about 9:55 p.m.

Airbags and seat belts were credited by firefighters as sparing the BMW's two occupants serious injuries.

The two occupants of the Ford Escape, which apparently was rear-ended, also were wearing seatbelts. The SUV's airbags deployed on impact in the crash.

Traffic was confined to one lane for the duration of the incident. The last Fire Department unit left the scene about 11:10 p.m.

State Police are investigating the cause of the accident.