California State Route 156
|Defined by S&HC § 456|
|Maintained by Caltrans|
|Length:||25 mi (40 km)|
|West end:||SR 1 near Castroville|
|East end:||SR 152 near Hollister|
Route description 
The western terminus is at State Route 1 in Castroville. The eastern terminus is at State Route 152 near Hollister. It overlaps U.S. Route 101 for 8 miles (13 km) between Prunedale, and San Juan Bautista. Route 156 passes through Monterey, San Benito, and Santa Clara Counties. Along with US 101, it is the quickest route from the San Francisco Bay Area to the Monterey Peninsula.
For its westernmost two miles (3 km), Route 156 is a freeway through Castroville, terminating at a Y-interchange with the Route 1 freeway. There is no direct access from Route 156 West to Route 1 North or Route 1 South to Route 156 East. Motorists who want to go from Route 1 South to Route 156 East can do so by using Route 183 South through Castroville. Traffic heading west on Route 156 can access Route 1 North by exiting at the Route 183 interchange and heading north.
The original portion of the route was defined in 1909 and ran from U.S. Route 101 to Hollister. In 1933, the remainder of the route (between Castroville and US 101 and between Hollister and Route 152) was added. It was signed as Route 156 by 1963, but was not part of the original 1934 state signage of routes.
|This article is outdated. (October 2010)|
Highway 156 experiences heavy truck traffic as it serves as a primary route for moving people and goods between the Monterey Peninsula and the rest of the state. It directly links with Highway 152, one of a small number of passable routes across the Coast Ranges between Monterey Bay and the Central Valley.
Monterey County 
The westernmost segment from Highway 1 to Highway 101 in Prunedale is a heavily traveled 2-lane section that has experienced numerous fatal crashes in recent years. Environmental studies are underway to upgrade this 5-mile (8 km) section to either a 4-lane highway or fully controlled access expressway. The Transportation Agency for Monterey County and Caltrans have narrowed the list of upgrade alternatives to one freeway and one expressway option. Alternative 11 — the expressway option — will add a second carriageway to the existing road. Interchanges will be constructed at Castroville Boulevard and Cathedral Oaks Road, while Oak Hills Drive will be an at-grade intersection. Alternative 12 — the freeway option — will build a new freeway to the south of the existing roadway with an interchange at Castroville Boulevard. Under this alternative, there will be no interchange with Cathedral Oaks Road or Oak Hills Drive. The existing Route 156 would be converted to a frontage road providing access to Cathedral Oaks Road and Oak Hills Drive. The environmental studies are expected to be complete in 2009, with the project slated for completion in 2015.
San Benito County 
San Benito County and Caltrans are conducting environmental studies for widening Highway 156 from two to four lanes between Highway 101 near San Juan Bautista and the Santa Clara County line. Interchanges are proposed with Highway 25 northwest of Hollister, Business Route 156 both north and southwest of Hollister, and Highway 101. The entire segment may be upgraded to freeway status to eliminate delays caused by numerous traffic lights currently present in the Hollister area.
Major intersections 
Except where prefixed with a letter, postmiles were measured on the road as it was in 1964, and do not necessarily reflect current mileage. R reflects a realignment in the route since then. The numbers reset at county lines; the start and end postmiles in each county are given in the county column.
MON R0.17-101.32[N 1]
|R0.17||SR 1 south – Monterey Peninsula||Westbound exit and eastbound entrance|
|Castroville||R1.11||SR 183 to SR 1 north – Castroville, Salinas|
|East end of freeway|
|Prunedale||Prunedale Road||Interchange westbound; at-grade intersection eastbound|
|US 101 south / Vierra Canyon Road – Los Angeles||Interchange; west end of US 101 overlap|
|96.14[N 1]||337||San Miguel Canyon Road (CR G12)||Interchange|
|100.39[N 1]||Dunbarton Road to San Juan Road (CR G11) – Aromas, Watsonville||No eastbound entrance|
|San Juan Road (CR G11) – Aromas, Watsonville||No eastbound exit|
SBT 0.00[N 1]-R18.43
|West end of freeway on US 101|
|East end of freeway on US 101|
|US 101 north – San Jose, San Francisco||Interchange; east end of US 101 overlap|
|San Juan Bautista||3.02||CR G1 (The Alameda)||West end of CR G1 overlap; former US 101|
|7.25||Union Road, Mitchell Road|
|CR G1 (San Juan Road, SR 156 Bus. east) – Hollister||East end of CR G1 overlap; former SR 156 east|
|R11.37||SR 25 (Bolsa Road) – Gilroy, Hollister|
|R13.22||San Felipe Road (SR 156 Bus. west) – Hollister||Former SR 156 west|
|R0.60||SR 152 east – Los Banos||Interchange; eastbound exit and westbound entrance|
- Indicates that the postmile represents the distance along US 101 rather than SR 156.
- January 1, 2006 California Log of Bridges on State Highways
- CA Codes (shc:260-284)
- TAMC Highway 156 Upgrades
- California Department of Transportation, State Truck Route List (XLS file), accessed February 2008
- California Department of Transportation, Log of Bridges on State Highways, July 2007
- California Department of Transportation, All Traffic Volumes on CSHS, 2005 and 2006
- California Department of Transportation, California Numbered Exit Uniform System, U.S. Route 101 Freeway Interchanges, Retrieved on 2009-02-14.