axles, and inboard of it are three powered axles. Two of these articulated sets are placed back to back and connected by a hinge. The Pennsylvania Railroad's GG1 electric locomotives were notable examples of this arrangement. 2+C-C+2 "2+C-C+2" means there are two sets of axles under the unit. Within each of these sets, there is a guiding truck with two idler axles, and inboard of this, and hinged to it, is a truck with three powered axles. The GE steam turbine-electric locomotives of 1939 were notable examples of this arrangement. 2-C1+2-C1-B "2-C1+2-C1-B" means there are five trucks. Only the first three axles on the four-axle trucks were powered, as were both axles in the last truck; the first and middle trucks had two unpowered axles each. The only examples of this arrangement were three unique coal-fired steam-turbine locomotives built by the Baldwin Locomotive Works for the Chesapeake and Ohio Railway between 1947 and 1948. This locomotive is sometimes called the M-1. C-C+C-C "C-C+C-C" means there are four trucks under the unit. Each truck has three powered axles. The only examples of this type were the 8500 horsepower (6.3 MW) turbine locomotives built by General Electric for Union Pacific. These locomotives consisted of two permanently coupled C-C units. C+C-C+C "C+C-C+C" means there are four trucks. Each truck has three powered axles and pairs of them are connected by span bolsters. This arrangement was used on the Jawn Henry coal-fired steam-turbine locomotive built by the Baldwin Locomotive Works for the Norfolk & Western Railway in May, 1954. 1-D-1 "1-D-1" means there are three trucks under the unit. At either end are trucks with one idler axle; the center truck has four powered axles. The original 1904–1909 New York Central S-Motor third-rail electric locomotives (for the Grand Central Terminal electrification) and the Great Northern Z-1 electric locomotives (for the Cascade Tunnel electrification) used this arrangement. 2-D-2 "2-D-2" means there are three trucks. At either end are trucks with two idler axles; the center truck has four powered axles. The PRR R1 electric locomotive used this arrangement. D-D "D-D" means there are two trucks. Each truck has four powered axles. Examples include the EMD DD units. D-D locomotives so far have fallen out of favor as nearly all of these have been twin-engined locomotives, which placed too much horsepower in too few axles, thereby making these consists rather inflexible (each locomotive featured two prime