A 57-year-old Honolulu woman was critically injured in a pedestrian crash just before 7 p.m. Monday. She was struck on Kokea Street, south of North School Street while walking in the roadway.  Police say the woman was walking in the street, because several garbage cans were blocking the unimproved sidewalk. She was taken to the hospital in critical condition with head injuries.   The 64-year-old driver of the vehicle that struck her was not injured.  Police say speed, drugs and alcohol were not factors in the crash.