on June 21, 1937. Most of this extension used the Midland Trail, although the route entered California from Nevada slightly north of the previous route of the Midland Trail, instead passing through Bishop. While being designated US 6, parts of modern SR 14 were upgraded to freeway standards. As part of the 1964 state highway renumbering, US 6 was truncated at Bishop. The portion of US 6 from Inyokern to Los Angeles was designated SR 14. Previously, the SR 14 designation was used for Artesia Boulevard and Lincoln Avenue, in the Los Angeles area, a portion of modern SR 91. Between 1963 and 1975, significant portions of US 6/SR 14 were moved to a freeway alignment. The former routing south of Mojave (and the current routing to the north) is still known as Sierra Highway. The first freeway section, from just east of Solemint Junction to Red Rover Mine Road, was completed in 1963. Further portions in the intercanyon areas of Acton to Soledad Pass were completed by 1965. By 1966, the freeway was complete as far north as Avenue P-8 (now Technology Drive) in Palmdale. The freeway was completed to Mojave by 1972. Incidents The Newhall Pass interchange, where I-5, Sierra Highway, Foothill Boulevard, San Fernando Road and the southern terminus of SR 14 meet, has been the site of a number of catastrophic incidents. The interchange has partially collapsed twice due to earthquakes: the 1971 Sylmar earthquake and the 1994 Northridge earthquake. As a result of the 1994 collapse, this interchange was renamed the "Clarence Wayne Dean Memorial Interchange", honoring a Los Angeles Police Department motorcycle officer killed when he was unable to stop in time and drove off the collapsed flyover ramp from SR 14 south to I-5 south. After both earthquakes, the collapsed portions were rebuilt and surviving portions reinforced. In 2007, two tractor-trailer trucks collided in a tunnel along the truck lanes for southbound I-5 at the interchange. A resulting fire started, soon encompassing the entire tunnel along with 30 other trucks and one passenger vehicle that were in the tunnel at the time. The truck tunnel was closed for several days for structural damage inspections and repairs. Cancelled plans SR 14 is an unfinished route, as the definition in the California Streets and Highways Code states that the route begins at SR 1 (Pacific Coast Highway), near Sunset Boulevard in the Pacific Palisades area