All lanes of Highway 17 were shut down Thursday morning at 9:43 after a dump truck hit a power pole at Bear Creek Road causing power lines to fall across the highway.
Commuters are being advised to take alternate routes between Santa Cruz and Santa Clara counties.
Signs on Highway 1 in Santa Cruz are advising motorists that the highway is closed at Idylwild Drive and to take Highway 129 to 101 to go northbound.
Southbound lanes reopened at 11:30 a.m.; one northbound lane is open.
At 1 p.m., CHP estimated that it would be another one to two hours before the second northbound lane will be reopened.