of doors on each side, one in the center and one at each end adjacent to the operator cab. The cars' exteriors originally had orange and red stripes along the sides, but these stripes were removed when RTA changed to a red, white, and blue color scheme. 20 of the cars are operable in single units, and they are numbered 181-200. The other 40 cars are operable in pairs, and they are numbered 301-340. The current fleet of Red Line cars underwent an in-house rehabilitation under the direction of the former director of rail Michael Couse. The cars were overhauled over the course of five years using federal grant money. Cars received pantographs and controllers, along with rebuilt trucks, traction motors, resistor banks, new flame-retardant flooring, LED lighting, new seat frames, revised interior paneling, and additional open space for improved ADA compliance. The first of the rebuilt cars was unveiled to the public on December 10, 2013. The current cars represent the third generation of cars that have been used on the line. The line opened using a fleet of shorter cars manufactured by the St. Louis Car Company in 1954 and 1955. The cars were long with blue and gray exteriors and are often referred to as "Blue Birds." They were virtually identical to the cars built by St. Louis Car at the same time for what is now the MBTA's Blue Line. Twelve cars were operable as single units with cabs at each end, and 56 cars operable as pairs. The single units were numbered as 101–112, and the paired units as 201–256. Additional cars in this fleet were purchased in 1958 when the line was extended to West Park. These comprised six additional single unit cars (numbers 113–118) and 14 additional double unit cars (numbers 257–270). When the extension to Hopkins Airport was being built in 1967, a fleet of 20 longer cars was purchased to supplement and replace the Blue Birds. These second-generation cars, numbered 151–170, were long and were built by Pullman-Standard Car Manufacturing Company. The cars, which had a stainless steel exterior with red and white trim and featured interior luggage racks, were promoted as "Airporters." The Airporters supplanted the Blue Birds, except during rush hour when extra cars were needed. In 1970, ten additional Airporters were purchased, numbered as 171–180. With the purchase of the Tokyu cars in 1985, all Airporters and Blue