In California's Central Coast region, the $130.7 million San Benito Route 156 Improvement Project is on track for completion this fall. The California Department of Transportation (Caltrans) project is constructing approximately 5 new miles of four-lane, at-grade expressway in San Benito County.
The new roadway is being built adjacent to the existing State Route 156 (SR 156) alignment, extending from The Alameda in San Juan Bautista, California, to Business Route 156 near Hollister, California. Project components also include a new roundabout at the intersection of Bixby Road and SR 156, as well as reconstruction of the intersection of Union Road and SR 156, which will improve access to and from the highway.
SR 156 plays a vital role in San Benito County’s transportation network, serving as a key east-west connector between California’s Central Coast, Bay Area, and Central Valley, making it a critical corridor for regional mobility. The route is essential to the movement of agricultural goods across the region, state, and nation. For residents, SR 156 is also a primary commuter route to nearby job centers, and its importance continues to grow as the county’s population increases. The corridor also serves as a gateway to major tourist destinations.
The annual average daily traffic (AADT) along the corridor is 33,000 vehicles. The projected AADT in 2042 is 42,900 vehicles, reflecting an anticipated 1.5 percent annual growth year over year. With its high volume of mixed traffic, SR 156 has experienced growing congestion and safety concerns.
“The SR 156 Improvement Project is a critical highway infrastructure project in San Benito County that is working to address longstanding issues of congestion, safety, and limited capacity along one of the region’s most important corridors,” said Terry Thompson, Caltrans District 5 Project Manager.
| Your local Case Construction Equipment Inc dealer |
|---|
| Monroe Tractor |
| Beauregard Equipment |
“Previously, SR 156 between the cities of San Juan Bautista and Hollister was a two-lane, local highway that experienced heavy traffic from commuters and freight vehicles, often resulting in bottlenecks, delays, and a higher risk of collisions. With the San Benito County’s population and economic activity on the rise, the existing roadway was no longer adequate to meet current and future travel demands.
“The project will expand SR 156 to a four-lane expressway, improving traffic flow, reducing travel times, and enhancing overall safety. The project is anticipated to close a major gap in the regional expressway system and support local and regional mobility by providing more efficient access between U.S. Highway 101, Hollister, and other key destinations. It will also benefit the local economy by facilitating the movement of goods, particularly for the critically important local and regional agriculture industry.”
Thompson said that the project is expected to reduce peak hour traffic congestion delays by an estimated 1,902 hours daily and 694,257 hours yearly, save an estimated $34.6 million in accident and vehicle operating costs over 20 years, and provide a $102.8 million return on investment in 20 years.
The project’s cost of $130.7 million is funded through local developer Traffic Impact Fees, local transportation sales tax Measure G (approved by voters in 2018), State Transportation Improvement Program funds, and additional federal funds.
| Your local Volvo Construction Equipment dealer |
|---|
| Tyler Equipment |
“The SR 156 Improvement Project includes several major components designed to enhance safety, reduce congestion, and improve regional connectivity between San Juan Bautista and Hollister,” said Farrukh Sana, Caltrans District 5 Construction Resident Engineer.
“At the heart of the project is the construction of 5 miles of new expressway, running just south of the original SR 156, which will provide a continuous and more efficient route from U.S. 101 to Hollister. The new highway is paved with continuously reinforced concrete pavement that has a 40-year life cycle versus a 20-year life for asphalt pavement, which the old highway used.
“A new double-lane roundabout has been built at Bixby Road. The eastbound and westbound directions will be separated by a 30-foot median divider, which the previous local highway did not have. Additionally, critical local access roads, including Mitchell Road/Bixby Road in Hollister, were realigned to connect with the expanded expressway, which required short-term, temporary closures during construction.
“Other features include a retaining wall, a new bridge over San Juan Creek on the eastbound side, a replacement bridge at Mission Vineyard over East Ditch, and access roads to adjacent farmlands.”
| Your local Hyundai dealer |
|---|
| Equipment East |
Construction began in August 2022 and is anticipated to be completed in the fall of 2025. The primary contractor is Teichert Construction of Pleasanton, California.
According to Thompson, phasing the construction of an expressway to minimize traffic disruption requires careful planning and coordination.
“Caltrans carefully studied existing traffic patterns during design of the project, which helped SR 156 engineers develop a detailed construction staging plan,” Thompson said. “For approximately the first two years of construction, crews were able to clear and build the new expressway lanes and roundabout just south of the original SR 156, largely un-impeding daily traffic.”
“Major excavation work was completed on the hillside alongside Union Road,” Sana said. “The material removed was used to raise the Union Road roadbed for the future realigned intersection. The hillside was recontoured to ensure it appeared to naturally fit in with the others around it. Major bridge work was completed at Mission Vineyard Road and over the San Juan Creek, and retaining walls and sound walls were constructed during this time.
| Your local Bobcat dealer |
|---|
| Bobcat of Boston |
“To protect both the construction teams and the traveling public, k-rail was placed along much of the project area, and lane widths were reduced to provide proper construction access and create space to construct eventual necessary tie-in work. Between mid [to] late 2024, crews executed short-term closures of major north-south connector roads, such as Union Road/Mitchell Road in Hollister, to align them with the future, widened expressway lanes. The roundabout was also completed by this point in time.”
In October 2024, construction crews conducted a major traffic switch from the original SR 156 to the newly constructed expressway lanes. Both directions are currently traveling on the south side of the new expressway, with one lane in each direction, while crews complete final construction and tie-in work on the north side.
“Currently, crews are preparing the new expressway to open to four lanes of traffic (two in each direction), completing drainage and grading work as weather permits,” Sana said. “This spring and summer, crews are completing paving work at west and east ends of the project, installing final signage, and constructing median barrier throughout. Once this work is complete, the final paving delineation will be implemented. Crews are also helping to repair and transition the original SR 156 in preparation to turn over to the County of San Benito.”
For the intersection of Bixby Road and SR 156, the decision was made to utilize a roundabout design because, according to Thompson, roundabouts “reduce the likelihood of severe collisions, such as head-on or T-bone collisions, by allowing smoother, continuous movement of vehicles.”
| Your local Trimble Construction Division dealer |
|---|
| SITECH Northeast |
“This design is more efficient than traditional traffic signals, reducing delays and congestion, particularly during peak times,” Thompson said. “As traffic volumes increase with regional growth, the roundabout will better handle higher traffic loads. Additionally, roundabouts require less maintenance, reduce fuel consumption, and lower vehicle emissions, making them a cost-effective, environmentally friendly solution.”
The project has addressed several construction challenges, with weather being one primary factor.
“Major weather events had a significant impact on the project's timeline and logistics,” Sana said. “One of the most disruptive factors was the series of heavy rainstorms that struck central California during the winter months between 2022/2023 and 2023/2024. These storms, often driven by atmospheric rivers, led to widespread flooding in low-lying areas near the project corridor.
“Construction zones became inundated with water, requiring short delays on planned construction work. Saturated soils delayed earthwork and required additional stabilization efforts to ensure long-term roadbed integrity. Persistent wet conditions causing erosion required continual repairs, drainage work, and additional erosion control.”
| Your local Wirtgen America dealer |
|---|
| United Construction & Forestry |
| WI Clark |
Coordinating the work with the needs of the public, and minimizing disruptions, has also been a significant concern.
“The construction team has worked very closely with the Caltrans Public Information Office team to disseminate project information and address public inquiries and construction challenges,” Thompson said.
“Early in the project, during initial clearing and grubbing, community members in San Juan Bautista expressed concerns about a grove of old growth Redwood trees. Hearing these concerns, the construction team worked closely with a certified Forester to evaluate an approach to ensure the trees survived construction, changing construction plans and redesigning drainage systems.
“Additionally, planned work and associated closures at Union Road and Mitchell Road were accelerated to minimize disruption to the public after feedback during a quarterly interagency construction/update stakeholder meeting. The construction team worked extended hours and working days to meet the milestone dates to open these roads to the public in a timely manner.”
| Your local Esco Corporation dealer |
|---|
| Genalco |
Other challenges included:
- Soil conditions/ground treatment: At the start of the project, the construction team encountered extremely saturated ground conditions due to the irrigation water from the adjacent farmlands. Almost 3 miles of new roadway footprint had to be lime treated to stabilize the ground.
- PG&E gas transmission and power line relocations: Earthwork at the Union Road hillside had to be closely coordinated with PG&E due to the need to relocate gas transmission lines. In addition, several PG&E overhead powerlines and pole relocation were relocated ahead of construction to minimize disruption to construction.
- AT&T fiber optic line relocation: Construction crews had to closely coordinate with AT&T, who needed to relocate fiber lines during construction.
- Environmental and regulatory permits: The project site is habitat for several protected species like red-legged frogs and tiger salamanders. Caltrans biologists regularly monitored construction progress to comply with the permit requirements and to assure protection of the protected species.
The SR 156 Improvement Project is a critical investment in the region’s future, supporting local growth, tourism, and economic development in San Benito County.
“By expanding SR 156 from a two-lane highway to a four-lane expressway, the project will significantly improve traffic flow and reduce congestion between U.S. Highway 101 and Hollister,” Thompson said. “This not only benefits daily commuters and freight operators but also enhances access to local businesses and job centers, making the area more attractive for employers and entrepreneurs.
| Your local Case Construction Equipment Inc dealer |
|---|
| Monroe Tractor |
| Beauregard Equipment |
“Additionally, SR 156 serves as another link between the Bay Area and popular destinations such as Pinnacles National Park, Mission San Juan Bautista, and the Monterey Bay region. Improving this corridor will help boost tourism by making travel safer and more efficient for visitors. The project also includes important safety enhancements, such as a divided and median protected roadway, which will reduce collisions and improve overall travel reliability.
“This project aligns with long-term growth and planning goals for San Benito County, ensuring the region can continue to develop sustainably while improving quality of life for residents and travelers alike. Overall, this project represents a major step forward in creating a more connected, accessible, and economically vibrant region.”
Photos courtesy of the California Department of Transportation
