3 kV DC is used in Belgium, Italy, Spain, Poland, the northern Czech Republic, Slovakia, Slovenia, South Africa, Chile, and former Soviet Union countries (also using 25 kV 50 Hz <answer>AC</answer>). It was formerly used by the Milwaukee Road from Harlowton, Montana to Seattle-Tacoma, across the Continental Divide and including extensive branch and loop lines in Montana, and by the Delaware, Lackawanna & Western Railroad (now New Jersey Transit, converted to 25 kV <answer>AC</answer>) in the United States, and the Kolkata suburban railway (Bardhaman Main Line) in India, before it was converted to 25 kV 50 Hz <answer>AC</answer>.
What does the railway system of US use DC or AC?
AC