sentences:  For this reason, the Birneys were also called "safety cars".Another critical feature of the Birney in dealing with safety issues from the critics of one-man operation was its compact size which eased the motorman's view of the road and reducing the number of doors to a single one.In the US, regardless of various technological solutions to resolve the safety issues of one-man operation, there was consistent resistance towards one-man operation among the motormen and conductors of the streetcars.