The New York Central has been, as we shall see in greater detail in the chapter on the coming of electricity, the first of the standard steam railroads entering New York to provide suburban trains of multiple unit motor-cars, similar to those used in rapid transit subway and elevated trains. The great advantage of these trains over trains handled by either steam or electric locomotives is an operating advantage. The train may be so quickly turned in terminals as to bring the terminal problem down an appreciable percentage, and so to give a greater hauling capacity to main-line tracks. The Central, wedged in tightly by the high hills that lie to the north of the metropolis, has had to pin its faith to plans that utilize the present tracks to the uttermost capacity. The railroads crossing New Jersey and reaching the west bank of the Hudson have not been behind the routes that enter from the north in providing for the suburban business. The recently opened McAdoo Tunnel, linking the Jersey terminals of the Erie, the Lackawanna, and the Pennsylvania with both the downtown and the uptown theatre, hotel, and shopping district of Manhattan, has been a great stimulus to the suburban development across the Hudson. The Lackawanna has done its part by boring a second tunnel under the Bergen Hill, parallel to its original tube, giving a four-track entrance to its fine new terminal, and relieving the congestion of suburban traffic night and morning at its worst point, the neck of the bottle. The Erie has already completed, as a part of its extensive terminal reconstruction-work in Jersey City, a similar project, a four-track open cut through the stout backbone of Bergen Hill. The open cut replaces completely the so-called Bergen Tunnel, which has already become a matter of history.