Question: What was the common abbreviation for the railroad by which the Cricket Tunnel and Crest Tunnel were built?

<P0-S0> The Simpson Tunnel, so named for the Simpson Farm it passed under, was a railroad tunnel originally built in 1903 by U.S. Steel and subsequently used by the Dunlap Creek branch of the Monongahela Railway. <P0-S1>  The tunnel was made of stone with a brick arch construction. <P0-S2>  The line was utilized both to serve coal mines and coke works in the area and to interchange with the Baltimore and Ohio Railroad's Fairmont, Morgantown and Pittsburgh line and the Pennsylvania Railroad's Coal Lick Run branch. <P0-S3>  The last move on that line, and thus through the tunnel, was on November 6, 1975. <P0-S4>  The line was subsequently abandoned by 1976 and the real estate disposed, however the tunnel was not destroyed or blocked at the time. <P0-S5>  At some point between 2008 and 2010 the tunnel was destroyed, likely due to the construction of the Mon-Fayette Expressway. <P0-S6>  It is not clear whether the tunnel was blasted or simply filled in. <SEP> <P1-S0> The Portland and Southwestern Railroad Tunnel, also known as the Nehalem Divide Railroad Tunnel, is an abandoned railroad tunnel near Scappoose, Oregon, United States, that is listed on the National Register of Historic Places. <P1-S1>  The tunnel was driven by the Portland and Southwestern Railroad, whose chief business was logging. <P1-S2>  Unusually for a logging railroad, the Portland and Southwestern built tunnels. <P1-S3>  In order to reach the far side of the Nehalem divide in the Northern Oregon Coast Range, the railroad undertook a 1712 ft tunnel. <P1-S4>  Some work was started in 1910, but most work began in 1918 and was completed in 1919. <P1-S5>  Since the tunnel was not through solid rock, the tunnel was lined with timber. <P1-S6>  The tunnel was used until 1945, when it was replaced by a truck road over the divide. <SEP> <P2-S0>  MoPac was a Class I railroad growing from dozens of predecessors and mergers, including the St. Louis, Iron Mountain and Southern Railway (SLIMS), Texas and Pacific Railway (TP), Chicago and Eastern Illinois Railroad (C&EI), St. Louis, Brownsville and Mexico Railway (SLBM), Kansas, Oklahoma and Gulf Railway (KO&G), Midland Valley Railroad (MV), San Antonio, Uvalde and Gulf Railroad (SAU&G), Gulf Coast Lines (GC), International-Great Northern Railroad (IGN), New Orleans, Texas and Mexico Railway (NOTM), Missouri-Illinois Railroad (MI), as well as the small Central Branch Railway (an early predecessor of MP in Kansas and south central Nebraska), and joint ventures such as the Alton and Southern Railroad (AS). <P2-S1> The Missouri Pacific Railroad (reporting mark MP) , commonly abbreviated MoPac, with nickname of The Mop, was one of the first railroads in the United States west of the Mississippi River. <SEP> <P3-S0>  The Crest Tunnel, at 3500 ft is the longest tunnel in Arkansas, and is its only curved tunnel. <P3-S1> The Cricket Tunnel and Crest Tunnel are a pair of railroad tunnels in northern Arkansas, near the city of Omaha in Boone County. <P3-S2>  Both tunnels were built by the White River Division of the Missouri Pacific Railroad in the early 20th century. <P3-S3>  The tunnels were listed on the National Register of Historic Places in 2007.