Drivers will encounter intermittent closures of the state Highway 1/state Highway 17 connector ramps in Santa Cruz.
Through much of the late morning and early afternoon, traffic has been backed up to Granite Creek Road/Scotts Valley Drive.
Drivers will likely experience delays.
The CHP said the collision was first reported around 3:35 a.m.
There are only four signal lights and one stop sign on the busy highway.
Residents may experience delays during construction.
A Sig-Alert was issued Tuesday morning for state Route 1.
The Santa Cruz Police Department has announced the areas that will receive special treatment during Halloween festivities.
The incident was reported at 9:26 a.m. Wednesday.
The project will rehabilitate/reconstruct Cedar Street from Church Street to Laurel Street and is expected to conclude in early 2019.
The City of Santa Cruz is scheduled to close access to the Railroad Trestle Bridge beginning Wednesday, March 7.