Soon after "Silver Dome" entered service, railroad managers and passenger train executives met to discuss the merits of the dome car design. In the United States, domes could only be readily used on railroads west of the Mississippi, due to lower clearances in tunnels in the eastern USA. (In Canada, Canadian Pacific would run its domes from coast to coast.) The managers also noted that the passenger carrying space was regarded as non-revenue space because the managers believed that passengers would not want to spend their entire trip in the domes. These factors and the added costs of car construction in adding stairs, two levels of car floors and air conditioning increased the costs to railroads that chose to operate dome cars.