but in a vague way the now familiar pattern was recognized : a region of the city would be cut off from circulation by newly constructed thoroughfares that bypassed it ; businesses would depart ; disagreeable industries would move in , creating local noise and air pollution and further reducing the attractiveness of the area ; ultimately , no one with the means to live elsewhere would choose to reside in such a place , and the region would become decrepit , badly maintained , and overpopulated by the lowest classes .