roller bearings), but most 1960s units might be ordered with roller bearings. Fairbanks Morse entered the road switcher field in 1947 with the H-15-44. EMD was the last to enter the field and failed to capture much of the market with their first road switcher the BL2. The RS-3 was the best known of the Alco RS road switchers and was produced in more numbers than the RS-1 and RS-2 designs combined. Although Alco produced the first known road switcher, EMD's GP7 was probably the most successful model from this early period road switchers. Few or no EMD GPs and no EMD SDs were ordered with plain bearings, and any plain bearing-equipped GPs were later updated to incorporate roller bearings. Modern examples include the EMD SD70 series and the GE AC6000CW, one of the most powerful examples producing . Horsepower Road switchers may be divided into: Generation 1, or lower, net for traction; Generation 2, , net for traction; Generation 3, , net for traction; and Generation 4, or higher, net for traction. Although at one point , net for traction, units were made, these quickly fell into disuse, and most have been scrapped by North American railroads. The most common new units made today are , net for traction. Transmission Within the Americas, road switchers are almost always diesel-electric, with the "transmission" system (i.e., the final drive) being either direct current (standard performance units) or alternating current (high performance units). For economic and performance reasons, and lower units generally have a DC generator, producing 600 volts DC, nominal, whereas and higher units generally have an AC alternator with integral rectifier, producing 1,200 volts DC, nominal, (alternator/rectifiers remained an option on certain sub- units, for economic and service reasons). Units with AC final drive accept the 1,200 volts DC from the alternator/rectifier and invert this to 1,200 volts three-phase variable-frequency AC. United Kingdom The term "road switcher" is not used in the UK. The nearest equivalent is the type 1 locomotive of which there were 5 designs. None of these designs exactly match the Road Switcher. The British Rail Class 14 and British Rail Class 17 have the low engine covers, but the cab is located centrally. Two other designs had the cab near one end like the road switcher, i.e. British Rail Class 15 and British Rail Class 16. However the engine covers reach the cab roof level. The