A motorcyclist was killed in a crash early Thursday on northbound Interstate 5, near the Mercer Street exit in downtown Seattle.

The Washington State Patrol said the rider, a 52-year-old Arlington man, was killed when his 2001 Yamaha XVS65 veered left and struck the freeway’s left-shoulder barrier just before 6 a.m. Thursday.

State Patrol Trooper Rick Johnson said on Twitter that speed may have played a role in the crash.

Traffic backed up for miles as the highway was down to one lane for about three hours, according to police and transportation officials.

All lanes reopened before 9 a.m, but the traffic impact on the morning commute was significant, police said.