Nampa Police arrested Jeffrey L. Knutson about 5 p.m. Saturday on aggravated driving under the influence of alcohol and open container charges.
Police say Knutson, a 43-year-old Nampa resident, turned directly into the path of a motorcyclist near Northside Boulevard and 6th Street North.
The motorcyclist, a 38-year-old female resident of Nampa, was transported to a local hospital with serious injuries.
Knutson was driving a 2KrazyKabs cab and was on duty at the time of the crash, but he did not have any passengers.
Knutson has been booked into the Canyon County Jail and is being held without bond. He will be arraigned on Tuesday morning.