The incident happened around 3:30 a.m. as a 1998 Ford Explorer traveling southbound on I-495 collided with the right shoulder guardrail in the area of Edgemoor Road.
Police say the vehicle spun into the roadway where it became disabled.
Troopers were responding to that call when a 2009 Kentworth tractor trailer, also traveling southbound on I-495, struck the Explorer before striking the concrete barrier and steel wall in the center median.
Police say the driver, 70-year-old William Elam, was trapped in the rig for nearly an hour before firefighters were able to free him. He was transported to Christiana Hospital where he is listed in critical condition.
Police say another tractor trailer traveling southbound struck the unlit Ford Explorer a short time later before the roadway could be closed down.
The second tractor trailer was driven by 47-year-old Luis Alexander. He was not injured in the crash.
Police believe the driver of the SUV fled the scene.
The crash shutdown the southbound lanes of I-495 were shut down for close to 7 hours during the investigation and cleanup.
Police say debris from the crash fell onto the railway below and spilled diesel fuel onto the roadway.
Amtrak operations in the area of the crash were also shut down while debris was removed from the tracks.
DNREC was called in to control the diesel fuel spill from the tractor trailer's tanks.
Delaware Power and Electric were called in to inspect damaged high voltage electrical wires along the median.
The Collision Reconstruction Unit is continuing the investigation, and is asking anyone with information to call 302-834-2620.