As railroad passenger ridership declined in the late 1950s, some railroads retired dome cars due to the maintenance costs. Other railroads that had not purchased dome cars new bought them second hand. Illinois Central purchased several cars from Missouri Pacific and Canadian National bought several cars from Milwaukee Road, for example. Because of their enormous usage of sealed glass, the cooling of the cars required massive air conditioning capacity. Maintenance and repair of these cars was costly. Breakdown of the air conditioning system on the road, even in winter, could render a car unusable.