By Carlos E. CastañedaA truck struck and killed a woman on an electric scooter in downtown San Francisco on Friday morning, police said. The collision happened at about 8:18 a.m. on Market Street near Powell Street. The San Francisco Police Department said officers found the woman in the street with life-threatening injuries and began life-saving aid before medics arrived. Bicycles, e-bikes and scooters are permitted along designated bike lanes, while private vehicles and typical ride-share vehicles are prohibited along the downtown portion of Market Street. Rueca said the investigation was determining whether the vehicle involved had the proper licensing to operate on Market Street.