Two serious accidents rocked Westchester highways Friday, leaving one dead and at least two seriously injured.

The first accident involved a car flipping over on I-684 near exit 4 in Bedford. Police say the driver was speeding on the northbound side when the car flipped onto the guardrail and became airborne, landing in the southbound lanes. Both men in the car suffered serious injures and were airlifted to the hospital, where they remain in critical condition.

The fatal accident happened south of exit 27 on the Bronx River Parkway, near the Kensico Dam in Valhalla. Police speculate that a car attempted to change lanes and crashed into a motorcycle driving in the adjacent lane. The motorcyclist, who has not been identified, was pronounced dead at the scene. The driver of the car, also unidentified, was taken to the hospital with unknown injuries.