The two routes—US 6 and US 89—begin an overlap here that extends through the Spanish Fork Canyon, alongside the UP Provo Subdivision (ex-D&RGW), to Thistle in the Wasatch Range. The remainder of US 6 to the Colorado state line parallels this rail line (which becomes the Green River Subdivision at Helper). US 6 continues alone through the Spanish Fork Canyon, now alongside Soldier Creek, to Soldier Summit on the Wasatch Plateau, where it finally leaves the Great Basin into the watershed of the Colorado River. It begins to descend by following the White River, which empties into the Price River near Colton. The Price River takes US 6 down through the Price Canyon, the west edge of the Book Cliffs, joining US 191 at Castle Gate. The land flattens and opens out at Helper, named for the helper locomotives needed to carry trains up to Soldier Summit, and US 6 continues southeasterly around Price on a two-lane freeway bypass, with the old alignment marked as both a business route and SR 55. Relatively flat land continues as US 6 parallels the Book Cliffs to the southwest and west, crossing the Price River at Woodside. West of Green River, US 6 joins I-70/US 50, which it overlaps for the remainder of its stay in Utah. Now south of the Book Cliffs, the four routes head east to Crescent Junction, where US 191 splits to the south. As it begins to approach the Colorado River, the highway curves northeasterly through the Grand Valley and into Colorado. According to the National Highway Traffic Safety Administration, there were 519 fatal and serious injury crashes between Spanish Fork and Green River in Utah from 1996–2008, leading the stretch to be considered one of the deadliest roads in the U.S. US 6 forms an arch-shaped route with Spanish Fork at the apex. The western half of the arch is the road less traveled, passing through the Great Basin Desert, Sevier Lake, Delta, Eureka and the Tintic Standard Reduction Mill. The eastern half is a popular transportation corridor, paralleling the Denver and Rio Grande Western Railroad's transcontinental line. This half passes over Soldier Summit and the historic railroad hub of Helper. Starting in the spring of 1983, US 6 was a discontinuous route for almost one year, due to a massive landslide that destroyed the town of Thistle. During this time traffic was routed on two detours. One, via Salina, Utah, was over long and took traffic almost 100 aerial miles from the route of US 6.