The extension leads from the H-1 çAiea off-ramp by Aloha Stadium to the Moanalua Freeway on Red Hill.

Police arrested a man, 23, in Pearl City as a suspect.

According to initial police reports, the motorcyclist was hit at about 4:15 a.m. by a dark-colored pickup truck that drove away.

Firefighters from the Mokulele fire station provided emergency treatment to the motorcycle passenger.

Fire Capt. Wes Maxwell said the woman was treated for possible back injuries and was taken to The Queen’s Medical Center by city paramedics. She was later listed in serious condition.

Police shut down all eastbound lanes of the extension connecting the H-1 and Moanalua freeways at about 4:30 a.m. so traffic investigators could examine the area where the crash occurred.

The resulting traffic backup stretched all the way to the Waikele Shopping Center by 6 a.m.

Morning rush-hour traffic was diverted onto the H-1 Freeway’s airport viaduct. The freeway’s zipper and high-occupancy vehicle lanes were opened to all drivers to help accommodate the increased flow. The closed lanes were reopened at about 9 a.m.

The traffic death was the 38th of the year on O‘ahu, compared with 47 at this time last year.

Reach David Waite at 525-7412 or dwaite@honoluluadvertiser.com.