The Dalles Police Department says a man jumped from an Interstate 84 overpass into traffic, was hit by a vehicle, and died Thursday afternoon.  According to The Dalles Police Chief Patrick Ashmore, the incident occurred at about 2:50 Thursday afternoon.  Witnesses say it appeared the man jumped from the overpass at I-84 milepost 85 into oncoming eastbound traffic.  Police and medical personnel say the man was deceased when they found him lying in the roadway.  Eastbound Interstate 84 was closed for about 45 minutes while detectives conducted an investigation.