It happened before 11:00 a.m. on Street Road near Gravel Hill Road in Upper Southampton.
Police say 58-year-old Zinovi Pavlo of Warminster was hit after he stepped out from behind his disabled vehicle.
Medics pronounced him dead at the scene.
Images from Chopper 6 HD showed a long skid mark and a large dump truck stopped in the middle of the road.
An SUV with its hood up and emergency lights flashing was parked a short distance away on the right shoulder of the 2-lane divided highway.
Police say the 24-year-old driver of the dump truck stopped after the incident and was cooperating with investigators.
Though the investigation continues, police say this will likely be ruled accidental.