Officers were called to the northbound lanes of Route 110 near Interstate 395 around 9:15 p.m. on Nov. 8.
When they arrived, a driver of a sports car met police at the scene.
The driver stopped because he had run over Maddison Peterson, 22, who was lying in the roadway.
After further investigation, police determined that Peterson was likely standing in the roadway and was struck by an SUV or another vehicle high off the ground, authorities said.
A medical examination showed Peterson's injuries are consistent with someone who was hit by a larger vehicle than the one that stopped on the night of the accident.
Police are asking anyone who may have seen Peterson walking in the area shortly before the accident or who witnessed what happened to give them a call.