When it first opened, Metro ran a mix of four- and six-car trains; however, there have not been any four-car trains used in the system (except for the money train) since the mid-2000s. The most common train length is eight cars due to the fact that the 7000 series railcars can only be operated this way. During peak hours, a mix of six- and eight-car trainsets are used, while during off-peak and weekend hours almost all trains are only six cars in length. In 2008, Metro began planning to acquire sufficient quantities of the new 7000-Series cars to run 100% eight-car trains. Metro also tested eight-car trains on the Yellow and Blue lines in preparation for increased service during the 2009 inauguration of Barack Obama.