U-turns explained
A curved green arrow indicates that a u-turn is allowed in the manner and direction indicated by the arrow at that end of the segment.
When you hover the mouse over an allowed u-turn arrow, a small clock icon appears, which, when clicked on, allowed you to set scheduled u-turn restrictions, as well as vehicle type restrictions on the U-turn.
A curved red arrow with the slashed-circle icon indicates that a u-turn is not allowed (is restricted) in the manner and direction indicated by the arrow at that end of the segment.
A curved yellow arrow with a clock icon indicates the presence of scheduled (time-based) turn restrictions for the direction indicated by the arrow at that end of the segment.