Evaluation of Turbo Roundabout as a Tool for Congestion Mitigation and Safety Improvement in California

The proposal aims to evaluate the operational, safety, and environmental benefits of a planned turbo roundabout to be built in summer/fall of 2022 on State Route 25/Highway 156 in the City of Hollister, CA (Caltrans District 5). It will be the first turbo roundabout in CA (and only the second in the US, with the other under construction in Jacksonville, FL). 

Traditionally, the safety and operational assessment of intersection treatments rely on collision data from similar sites around the state (and the US). However, collision data-based approaches are reactive in nature. They require far too many crashes to occur over multiple years before the safety effectiveness of a treatment can be evaluated. Furthermore, since turbo roundabouts are pretty novel in the US, we plan to use innovative approaches in lieu of the traditional collision data-based analysis:
•    Proactive safety assessment using quantification of traffic conflicts using video analytics data.
•    Microscopic simulation modeling of the traffic operation through the State Route 25/Highway 156 intersection before and after the installation of the turbo roundabout.

Principal Investigator: 
Anurag Pande
PI Contact Information: 


Cal Poly San Luis Obispo

Impacts/Benefits of Implementation: 

The deliverables from this research will provide quantification of the benefits of turbo roundabout for the California context and a blueprint for practitioners in other Caltrans districts to consider this novel design for congestion mitigation and safety improvements.  We also plan to use the output from the analytical work to create materials for research dissemination to Caltrans staff in other districts and also for the general public.

Project Number: 



Contact Us

SJSU Research Foundation   210 N. 4th Street, 4th Floor, San Jose, CA 95112    Phone: 408-924-7560   Email: mineta-institute@sjsu.edu