Japanese industrial conglomerate Hitachi Ltd. is gearing up to expand its train system business in North America with the ongoing construction of a new assembly plant in Maryland. Hitachi held a groundbreaking ceremony last week for the plant in Hagerstown, Maryland, following its facilities in Florida and South Carolina that manufacture trains and signal systems. The new plant being built in a $70 million project is near the U.S. capital, where many train cars produced by Japan’s Kawasaki Heavy Industries Ltd. are already running in the subway system. Hitachi has signed a deal with the Washin…