The states conducted a study in mid-1925, which found that the Hudson River bridge would be able to pay for itself in twenty-five years if a 50-cent toll were to be placed on every vehicle. After funding was secured, surveyors began examining feasible sites for the future bridge's approaches in August 1925. By law, the New York end of the Hudson River Bridge could only be constructed between 178th and 185th Streets, and the New Jersey end had to be built directly across the river. Geologists made test bores on the New Jersey side to determine if the site was feasible for laying foundations for the bridge. Othmar Ammann was hired as the bridge's chief engineer. In Ammann's original plans for the bridge, which had been published in March 1925, he had envisioned that the bridge would contain two sidewalks; a roadway that could carry up to 8,000 vehicles per hour; and space for four railroad tracks, in case the two North River railroad tunnels downstream exceeded their train capacity. Cass Gilbert was hired in January 1926 to design architectural elements for the Hudson River bridge, including the suspension towers. The bridge design had yet to be finalized, and its cost could not even be estimated at that point due to the complexity of factors.