sentences:  At the same time a worldwide need was seen for a low-cost rail vehicle.The Research Division and British Leyland together produced a lightweight four-wheeled vehicle which they referred to as LEV-1.After proving trials, which included assessment on the Boston and Maine Railroad in America, it was developed into the Class 140 which led to a series of two-car "Pacer" units, and around 150 of various classes were built.