Authorities say 32-year-old Enrique Lopez of Moreno Valley was driving his 1996 Honda Accord westbound on the freeway when he veered into the right shoulder near 14th Street and struck the 37-year-old worker, who was setting traffic cones for a closure at about 9:30 p.m.
The highway worker was rushed to a local hospital with major injuries.
Authorities say after the crash, Lopez fled the scene. He was found about a mile away on Central Avenue. Lopez was arrested for felony DUI and booked at Robert Presley Detention Center.
The off-ramp and the two right lanes of the 91 were temporarily closed. The accident remains under investigation.