which places does the route connect?
Piru Canyon, Grapevine
Ridge Route
In 1929 the state decided to build a new bypass of the central portion through Piru Canyon, and to upgrade the north portion over Tejon Pass and down the hill to Grapevine. This Ridge Route Alternate, or Ridge Alternate Highway, shortened the route by and increased the minimum curve radius from . 
what does the term ridge route refer to? A two-lane highway between Los Angeles County and Kern County, California. who constructed it? California Highway Commission had the roadway faced any accident anytime? Yes - A Ridge Route Alternate was built to prevent road accidents and to increase road capacity.
wiki:17775748
Ridge Route [SEP] Bypasses and the fate of the bypassed road
In 1929 the state decided to build a new bypass of the central portion through Piru Canyon, and to upgrade the north portion over Tejon Pass and down the hill to Grapevine. This Ridge Route Alternate, or Ridge Alternate Highway, shortened the route by and increased the minimum curve radius from . This was done for the safety of the road, which had many accidents, and to increase the road's capacity. The old highway was to be relinquished to Los Angeles County and incorporated into the county road system. Construction began in 1930, and the road south of Tejon Pass opened on October 29, 1933; replacement of the Grapevine grade was completed in 1936.