Page:California Highways and Public Works Journal Vols 8-9.djvu/16

 Upper heavy line shows new route adopted for state highway on Ridge Route; lower barred line shows present location.

Under agreement with the board of supervisors of Los Angeles County, the present route will be taken into the Los Angeles County road system, and with the opening of the alternate route, the state will be relieved of further maintenance costs upon it.

The change has been approved by Attorney General Webb.

LOCATION OF NEW SECTION The termini of the relocated road will be at Castaic on the present highway to a reconnection with the state highway at Gorman, near Tejon Pass, a distance of 26 miles, and will effect a saving of 7.3 miles over the present route.

Exhaustive engineering study demonstrated that the most practicable location for this important artery connecting northern and central California and the region south of the Tehachapi Range is controlled by the Tejon Pass. The new location south of this pass differs from the present location by following drainage courses for a more direct southerly descent instead of traversing the ridges from which sudden descents must be developed on inferior grade and curvature. Thereby distance, curvature, adverse grades and steep grades are all reduced.

The grades on the alternate route are far more uniform and will have 1280 feet less elevation in rise and fall than the existing highway. The grade rates will be satisfactory for high gear operation. The minimum radius of curvature will be 1000 feet, a sweeping alignment satisfactory for legal speed limits. This curvature gives long distance with consequent safety and relief from the strain of guarding against surprises on the sharp curves that characterize the present road, on which a number of curves are built with a radius as sharp as 70 feet.

Traffic census shows a 40 per cent increase in travel over this section in the past three years, greatly overstressing the maximum economic capacity of the road. It is estimated that present travel will increase 175 per cent in the next ten years.

The Ridge Route was constructed in 1914 as one of the first projects undertaken by the California Highway Commission. The total motor vehicle registration of the state in that year was 125,516 as compared with a present registration of 2,015,418. The road follows the combs of the mountain ridges, adhering to contour alignment for economy in grading, in keeping as near as possible to the top of the ridges, several false summits are encountered on the route. Attempts to improve alignment have been made in the past at heavy cost, but the improvements have failed to do more than temporarily remedy defects, inherent in the original location. On the present routing, it has been found impossible to eliminate the general character of the continuous swing of reverse curves. The road is a marked example of the impossibility of adequately modernizing a location in a heavy mountain district with maximum grade on tortuous alignment. The condition of the road makes it unnecessarily detrimental to the proper flow of travel between northern California and the San Joaquin Valley on the one hand and Los Angeles and Southern California on the other.

The new route lies west of the present Ridge Route. It starts near Castaic Post Office. After crossing a flat country for several miles, it begins its a.scent on the west side of the canyon to pass over a saddle into Violin Canyon. The route crosses Violin Canyon to Violin Summit; thence it crosses Canton Creek and Oso Creek, and ascends Piru River and Liebre Creek to the divide between Liebre and Alamos Creeks. Thence it follows valley up Alamos Creek to a point 3 miles north of Baily Patrol Station on the present road. It effectually eliminates the portion of the Ridge Route containing the worst features of that road.