TRAVELING AT APPROXIMATLY 45 MPH ON SMOOTH PAVED ROAD. SUDDENLY SHOT TO LEFT INTO ONCOMING TRAFFIC. RESULTING IN SERIOUS INJURY. IT ALSO FELT AS IF THERE WAS A SUDDEN ACCELERATION. HOWEVER, EVERTHING OCCURRED IN AN INSTANT. SO, ACCELERATION MAY JUST BE PERCEIVED. WITNESS, FOLLOWING DESCRIBED SAME WAY TO PD.