suburbs in southern San Gabriel and Pomona valleys, it is a major transportation corridor. For the majority of its length, it is generally parallel to, and south of, the San Bernardino Freeway, I-10, and generally parallel to and north of the Riverside Freeway, SR 91. The rapid population growth exacerbates traffic congestion and, therefore, residential, commercial, and industrial development in the Inland Empire. In particular, it has become increasingly clogged of late with shipping container-laden trucks traveling from the ports of Los Angeles and Long Beach to rail yards and warehouses in the Inland Empire. As a result of the rapid development of the Inland Empire since the 1980s, the Moreno Valley Freeway now suffers from severe traffic congestion. In the mid-2000s, the northwestern section concurrently signed with Interstate 215 underwent significant construction to improve traffic flow, but it still suffers from heavy congestion. The freeway is known as the Pomona Freeway from its western terminus to its junction with SR 91 and I-215 in Riverside, and the Moreno Valley Freeway east of this interchange until its eastern terminus at its junction with I-10. The route is part of the California Freeway and Expressway System, and is part of the National Highway System, a network of highways that are considered essential to the country's economy, defense, and mobility by the Federal Highway Administration. History The route takes its number from former US 60, which now begins near Brenda, Arizona, and terminates on the east coast at Virginia Beach, Virginia. Before 1964, US 60 ran from Los Angeles to the Arizona state line, where it continued its nationwide trek, often overlapping US 99 and US 70 along the way. The advent of I-10 created a situation where, at one point, four different signed roads were routed along the state-maintained highway. In 1964, California implemented a plan to simplify its highway-numbering system, where one state highway had only one route number, and concurrencies were strongly discouraged. As a result, the US 60 designations (along with US 70 and US 99) were removed. I-10 (as Route 10) superseded US 60's alignment from Beaumont to the Arizona state line, even though the routing was only partly a freeway. This left the officially designated Route 60 from Beaumont to Los Angeles orphaned from its original U.S. Highway (which to this day begins at a point on I-10 several miles east of Quartzsite, Arizona). This new