A manager in Westinghouse’s Elevator Division happened to recognize that electric stairways were expensive to build as each was a custom-engineered job and service was a headache for the for the customer and the supplier because of the great variation in product. He was aware that planning of anew urban transit system would call for many escalators of large and varying length. He asked the central product design laboratory to develop an economical solution to this problem. Westinghouse Elevator, Management of Technological Innovation, KV Patri

What came out was the modular escalator  an arrangement where individual motors spaced along the flight would share the load of driving the steps rather than depending on a single massive drive unit at the bottom. With this arrangement, an escalator of any desired length could be made from standard parts. These could easily be made available from stock for service and repair. There were several inventions made on the mechanical execution of this idea that provided good patent protection. The development was carried off in record time and an initial order from Washington, DC Metro System was the start of a revised product line, a totally changed-over factory and a present dominant share of the market. While the basic idea was certainly not profound, nor the technology dazzling, there was a real advantage to the customer and to the producer. Westinghouse Elevator, Management of Technological Innovation, KV Patri