Erie-built. BNSF took delivery of ES44C4 locomotives with this type of truck in 2009. In the UK, the Class 31 uses this wheel arrangement. A1A-B+B "A1A-B+B" means there are three trucks. The first truck has three axles, with the center one unpowered. A pair of two-axle trucks, each with both axles powered, are connected by a span bolster under the rear of the unit. The only example to date of this arrangement was a single experimental EMD SDP45. B "B" means there are two powered axles under the unit. These axles are not articulated relative to other parts of the locomotive. This arrangement is only used on very small locomotives, such as the EMD Model 40. This arrangement is sometimes referred to as 0-4-0, the Whyte notation equivalent. B-1 "B-1" means there are two trucks. The "B" truck is under the front of the unit, and has two powered axles. The "1" truck is under the back of the unit, and has one idler axle. Examples include the three EMD LWT12 locomotives built by EMD in 1956. B-2 "B-2" means there are two trucks. The "B" truck is under the front of the unit, and has two powered axles. The "2" truck is under the back of the unit, and has two idler axles in a row. Examples include the three lightweight RP-210 locomotives built by Baldwin in 1956 and 1957 for use with Pullman-Standard Train-X equipment. B-A1A "B-A1A" means there are two trucks. The "B" truck is under the front of the unit, and has two powered axles. The "A1A" truck is under the back of the unit, and has one powered axle, one idler axle, and one more powered axle. Examples include some of the FM C-liners (most passenger units) built from 1950 to 1955, and the EMD FL9. B-B "B-B" means there are two identical trucks. Each truck has two powered axles, a currently popular configuration used in high-speed, low-weight applications such as intermodal trains and high-speed rail, as well as in switching. Examples include the EMD GP (General Purpose), EMD F-units, EMD SW1500, Acela Express Power Cars, Siemens Charger, Siemens ACS-64 and GE Genesis units. High speed ("time") freight trains, with guaranteed schedules often use B-B locomotives of 3,800 HP (950 HP per axle), but this application, too, has largely been replaced by higher-powered, 4,500 HP C-C locomotives (750 HP per axle). An American Colloquialism of