San Mateo’s Smart Corridor system continues construction on the U.S. Highway 101 merge as a part of the countywide project. With support from several regional agencies, the project aims to modernize traffic management by adding connected signals, cameras, and sensors across key routes.
“The goal is to make the road network smarter, not larger,” said Audrey Shiramizu, senior engineer for the project. “Better data and faster communication help us manage traffic before backups even form.”
Shiramizu works for the City/County Association of Governments of San Mateo County (C/CAG), the agency coordinating the Smart Corridor initiative alongside the California Department of Transportation (Caltrans) and local cities. Her team oversees the planning, engineering, and implementation of intelligent transportation systems for the whole project.
“This system isn’t just about technology, it’s about making daily travel easier and safer for everyone in the county,” Shiramizu said. “Even when drivers don’t see it, the improvements are helping traffic flow more smoothly and efficiently.”
Construction for the Smart Corridor project began in 2018, starting with the southern segment, which runs from East Palo Alto to San Bruno. Since then, the system has gradually expanded, with new segments in South San Francisco, Brisbane, Daly City, and Colma currently under construction and expected to be completed by 2026.
“The southern segment has been operating successfully for several years, and now we’re bringing the same technology to the northern cities,” Shiramizu said. “Each new section allows us to coordinate traffic better and respond quickly to incidents across the county.”
Reina Subramanian, a senior at Carlmont High School, has noticed the impact of traffic firsthand. She also welcomed the county’s use of technology to improve traffic flow.
“Being stuck in traffic makes me anxious and stressed, especially when I’m running late,” Subramanian said. “It’s reassuring to know the city is investing in smarter systems to make our commutes faster and safer.”
The Smart Corridor relies on a combination of cameras, sensors, connected traffic signals, and underground fiber-optic networks to monitor and manage traffic in real time. The system allows cities and Caltrans to adjust signals, monitor congestion, and respond quickly to incidents on local streets and the freeway.
“When drivers understand how the system works and how it interacts with traffic flow, they can actually work in synergy with it, which improves both safety and efficiency,” said Alexandre M. Bayen, professor of electrical engineering and computer sciences at the University of California, Berkeley.
Beyond traffic management, the Smart Corridor’s infrastructure has potential uses that extend into other areas of public service. The underground fiber-optic network, installed initially to connect cameras and traffic signals, could support citywide services.
“We built all of this underground fiber for the Smart Corridor, but it can actually be used for a lot of other things beyond traffic management,” Shiramizu said.
One possibility is to provide public Wi-Fi access, similar to other cities that utilize municipal fiber networks to offer connectivity to residents and visitors. Other potential applications include energy-efficient bright lighting that can adjust automatically based on real-time conditions.
“The city of Oakland has been able to use a similar fiber network to provide free Wi-Fi across the whole city,” Shiramizu said. “We’re seeing a lot of new ways this countywide fiber could be used.”
The Smart Corridor project is a multi-agency effort that requires close coordination among local cities, Caltrans, and C/CAG. Each organization manages different parts of the system, from signal control to emergency response planning, but they all rely on shared data and communication to ensure smooth traffic flow.
“It’s very important that public agencies share data and coordinate,” Bayen said. “If you manage the whole system, you need access to the full set of information so decisions can be made quickly and effectively.”
The Smart Corridor project is funded through a combination of local, state, and federal sources, including transportation grants and regional development funds. The investment covers construction, technology installation, and ongoing system upgrades to ensure long-term reliability.
“Building a system like this requires a significant upfront investment, but the benefits in safety, efficiency, and future flexibility make it worthwhile,” Shiramizu said.
Maintenance and upgrades are a key part of the project’s plan, as sensors, cameras, and traffic signals need regular calibration and replacement. C/CAG and its partners have dedicated resources to ensure the system continues operating at peak performance.
“We’re constantly monitoring the infrastructure and updating software and hardware as needed,” Shiramizu said. “It’s not just about building it once; it’s about keeping it running smoothly for years to come.”
As construction continues at the U.S. 101 merge, San Mateo County is steadily expanding the Smart Corridor into a fully connected network designed to respond to traffic in real time. The work adds another layer to a system built on coordinated signals, cameras, and sensors that help operators manage congestion before it spirals.
“By integrating real-time data across the corridor, we can make travel safer and more efficient for everyone,” Shiramizu said.
