It happened around 8:00 p.m. in the southbound lanes near the 295 interchange.
Police say 36-year-old Twan Money was behind the wheel of a 2009 Chevrolet Aveo.
For an unknown reason, the car accelerated and changed lanes, striking the back of the tractor-trailer that was parked on the shoulder.
Upon impact, the car spun around and came to a stop in the center lanes of the highway.
A passing motorist happened to be a doctor and stopped to render aid until medics arrived.
Money was taken to Christiana Medical Center in critical condition. The driver of the tractor-trailer was not injured.
Delaware State Police continue to investigate.
