Seattle's monorail accident, in which two cars sideswiped each other on a curve, was caused by human error according to authorities. The Saturday evening accident, occurred when the inbound driver failed to yield to the other train where the tracks were too close together for passing, reported The Seattle Post Intelligencer. Eighty-four passengers were evacuated from the 43-year-old monorail, which spans a mile-long route between downtown and the Seattle Center. No serious injuries were reported. Officials have not been able to estimate when the monorail would resume service.