Police said 19-year-old Aaron Thomas had left his car parked in the safety zone of the expressway to buy gas on Commack Road.
Police said Thomas was coming back to his car when he was struck while crossing the entrance ramp to the expressway around 8 p.m. in Commack.
The 24-year-old driver of the car who struck Thomas stayed at the scene, police said.
Thomas, of Amityville, was taken to Huntington Hospital where he was pronounced dead.
No charges have been filed.
Newsday report Thomas was a freshman at Suffolk County Community College and was returning home from his first day on a new job.