A 20-year-old Middletown woman was killed this afternoon when her car collided with a tractor-trailer on the New York State Thruway in Hillburn.Police say the accident happened shortly before 12:30 p.m. when Lyssette Perez's car came speeding onto the shoulder of the road near exit 15A, where two trucks were parked. The vehicle was traveling northbound in the right lane and for some unknown reason, ran off onto the shoulder of the road and hit the back end of one of the trucks. The car got wedged underneath the truck, killing Perez. The drivers of the trucks were not hurt. Police are investigating what caused the accident, but say driver distraction is a possibility.