The Allegheny River in Pittsburgh is shut down to all traffic through March 1. But the difference-maker in this is the extreme cold sustained over this length of time.”The Allegheny River closure, which is called a “safety zone,” was issued Thursday by Capt. Justin Jolley, the Coast Guard’s captain of the Port of Pittsburgh, due to “ice conditions.”It includes the entire river, from mile marker 1 to mile marker 72. Ice on Pittsburgh’s iconic three rivers is currently ranging between 5 and 8 inches in thickness, according to Checkan. No end in sightAlthough the rivers have already seen ice this winter, Checkan said none of it had significantly impacted transit.