This Broadway Limited Union Pacific 4-8-8-4 Big Boy steam locomotive is based on the huge articulated engines used to haul trains up the UP's mountainous trackage west of Cheyenne, Wyoming, to Ogden, Utah. Often called the largest steam locomotive ever made, and certainly a contender for the world's most famous locomotive, the Big Boy was forged under some of the most strenuous demands ever placed on a locomotive. The UP Railroad needed a locomotive that could be used to pull a 3,600-ton train over Sherman Hill and the 1.14% grade from Ogden to Wasatch, Utah without the need for helpers. hen the design specifications were complete, it was decided on the use of a simple articulated, high speed, 132 ft. long locomotive sporting sixteen 68 diameter drive wheels. What they created was the longest and among the heaviest, most powerful steam locomotive legends in the world. And had not the worker at Alco chalked "Big Boy" on the front of the smoke box of one of the 4-8-8-4s under construction, a name that immediately caught on, it is rumored that the name of the type would have been Wasatch, for the mountains they were built to conquer. This model has full Paragon4 sound and DCC for realistic sound and motor control. The Paragon4 sound system works with all Broadway Limited Rolling Thunder(TM) advanced sound systems. Other features include a smooth-running flywheel-equipped drive, synchronized puffing smoke, installed engineer and fireman figures, directional lighting, traction tires for great pulling power and magnetic knuckle couplers. The 4-8-8-4 Big Boy can be operated on all DCC systems as well as on standard DC railroads (with limited sound functionality). This model has wheels profiled to operate on Code 70 and larger rail and curves of 18" radius but larger curves are recommended. The 4-8-8-4 Big Boy is one of many Broadway Limited HO Scale Paragon4 locomotives.