TUNNEL TO THE 21ST CENTURY

The current alignment of two-lane US 71 across the rugged Ozark plateau, between Ft. Smith and Fayetteville, Arkansas, was designed in the 1920s. With population, traffic, and trucking growth since the 1960s, this winding route has become known for travel delay and accidents. The Arkansas State Highway and Transportation Department proposed a new route in the 1970s, but it was not ubtil the late 1980s that environmental interests could be assuaged and construction began on a replacement highway for the old US 71 route. The replacement four lane divided highway is being built to Interstate standards. The maximum grade is limited to 5% and the minimum radius is 698 m (2291 ft). The new 69 km (43 mi) long roadway will consist of two 3.6 m lanes, with a 3 m right shoulder and a 1.2 m left shoulder. The combination of the high design standards and the rugged terrain necessitated choosing between either a massive cut or a tunnel. After considering initial costs and long term maintenance costs of both options, engineers decided to mine a .42 km lond, twin bore tunnel near Winslow, AZ.