A major Seattle traffic choke point is poised to make a dramatic change this weekend. But officials don't expect the soon-to-be two-way Mercer Street will improve the afternoon commute out of downtown. As of Monday, Mercer Street will carry two-way traffic for the first time since 1968. But The Seattle Times (http://is.gd/hfCJgX ) reports much more work remains to be done in the neighborhood. Automobile congestion eastbound toward I-5 isn't expected to improve much on the thoroughfare called "the Mercer mess" by commuters.