State Route 121 and 8th Street East Intersection Improvements Project
Enhancing operations, reducing traffic delays, and improving pedestrian and bicycle access.
Project Background and Existing Conditions
The intersection of State Route 121 and 8th Street East is a key regional corridor that experiences heavy commuter traffic and limited left-turn facilities, leading to congestion and operational challenges. To address these issues, the Sonoma County Transportation and Climate Authorities (SCTCA), in partnership with Caltrans District 4, Sonoma County, Sonoma County Regional Parks, and SMART, is advancing a project to improve safety, traffic flow, and multimodal access at this location.
Roundabout Alternative Summary
SCTCA is considering a modern roundabout alterative at the intersection. This alternative would replace the existing intersection of Route 121 and 8th Street East with a modern single-lane roundabout. It would ease traffic congestion by introducing traffic-calming and improving vehicle safety, and pedestrian and bicycle safety within and adjacent to the intersection.
 | Improved Operations & Traffic Flow | A modern roundabout is proposed to reduce delays, improve vehicle operations, and enhance overall functionality for all users. |
 | Better Walking & Biking Connections | The design supports future pedestrian and bicycle improvements, linking the Sonoma Schellville Trail and the San Francisco Bay Trail. These improvements include sidewalks and shared use pathways as well as on-street bike lanes. |
 | Anticipated Construction Cost | The current anticipated project construction cost is estimated to be approximately $16.9 million. |
 | Initial Assessment of Roundabout Alternative | The roundabout alternative calms traffic and provides superior operational and multi-modal connectivity benefits, fewer impacts, and cost significantly less than the signal alternative. |
 | Community-Driven | The project invites public input on this alternative, including any design elements like landscaping and signage. |
Signal Alternative Summary
SCTCA is also considering a signal alternative at the intersection. This alternative would convert the existing intersection of Route 121 and 8th Street East to a signalized intersection with curb, gutter, sidewalk, and pedestrian and bicycle improvements. Due to the need to accommodate turn lanes and acceleration/deceleration lanes, the project foot spans several hundred feet to the east and west of the intersection. Therefore, this alternative would also require the replacement of the Bridge over Schell Creek.
| Improved Operations & Traffic Flow | A traffic signal is proposed to reduce delays, improve vehicle operations, and enhance overall intersection functionality for all users. |
| Better Walking & Biking Connections | The design supports future pedestrian and bicycle improvements, linking the Sonoma Schellville Trail and the San Francisco Bay Trail. These improvements include sidewalks and on-street bike lanes. |
| Anticipated Construction Cost | The current anticipated project construction cost is estimated to be approximately $37 million. |
| Initial Assessment of Signal Alternative | The signalized intersection provides operational and some multi-use connectivity benefits, but it is significantly more costly and impactful to the community and surrounding environment. |
| Community-Driven | The project invites public input on this alternative, including design elements like landscaping and signage. |
Alternative Comparison
The following shows the results of the Intersection Safety and Operational Assessment on the two build alternatives:
| Analysis Criteria | Roundabout | Signal |
|---|---|---|
| Daily Vehicle Hours of Delay in 2050 | 14 hours | 34 hours |
| Daily Person Hours of Delay in 2050 | 25 hours | 60 hours |
| Life-Cycle Cost (Capital, Support, Environmental and Maintenance) over 20 years | $36.0M | $77.2M |
| Morning Peak Hour Delay and Level of Service (LOS) | 9.5 seconds / | 11.9 seconds/ |
| LOS A | LOS B | |
| Evening Peak Hour Delay and Level of Service (LOS) | 5.1 Seconds/ | 4.9 seconds/ |
| LOS A | LOS B | |
| Bicycle Facility Assessment | 0 potential safety concerns | 5 potential safety concerns |
| 0 potential comfort concerns | 11 potential comfort concerns | |
| Pedestrian Facility Assessment | 3 potential safety concerns | 4 potential safety concerns |
| 6 potential comfort concerns | 3 potential comfort concerns | |
| Total Bicycle and Pedestrian Facility Assessment Concerns | 9 | 23 |
| Benefit/Cost Ratio | 1.4 | 0.9 |
Potential Impacts and Environmental Document
The Environmental Document will be an Initial Study/Mitigated Negative Declaration (IS/MND) in conformance with the California Environmental Quality Act (CEQA) and a Categorical Exclusion (CE) in conformance with the National Environmental Policy Act (NEPA).
With both alternatives there will be impacts to some rights of way, wetlands, and will result in tree removals.
Due to the larger footprint of the signal, that alternative includes additional impacts to wetlands, additional right of way needs, more tree removals including established oak trees, impacts to Schell Creek and the potential impact to culturally sensitive areas.
Right‑of‑Way and Property Discussions During Environmental Review
As part of the environmental review process required under the California Environmental Quality Act (CEQA) and the National Environmental Policy Act (NEPA), the project team is currently evaluating potential environmental impacts and developing alternatives.
During this phase, agencies are not permitted to engage in specific discussions regarding potential right‑of‑way needs, property acquisitions, or parcel‑level impacts. This restriction is intended to ensure that the environmental process remains objective, unbiased, and free from any perception of pre‑determination.
Any property boundaries, staging areas, or potential impact zones shown in project materials are conceptual and subject to change as the environmental studies continue.
Once the environmental document is completed and a preferred alternative is selected, the project will move into the next phase, during which:
- Right‑of‑way needs will be finalized, and
- Direct outreach to affected property owners will occur in accordance with state and federal requirements.
We are committed to transparency throughout the process and will provide updated information as it becomes available.
Frequently Asked Questions (FAQ)
This FAQ responds to questions and concerns raised by community members during the February 2026 public open house and through written comments. Many questions focused on safety, driveway access, speeding, property impacts, and whether decisions have already been made. This document is intended to clarify what is being studied, why, and how community input will shape the next steps.
Why is SCTCA studying improvements at the SR 121 & 8th Street East intersection?
The SR 121 & 8th Street East intersection is a regionally important corridor that experiences heavy commuter traffic and long gaps between safe left-turn opportunities. Residents have reported difficulty and sometimes feel unsafe turning onto SR 121 from 8th Street East, particularly during morning and evening peak travel hours. There are currently no bicycle or pedestrian facilities at the intersection. The purpose of this project is to improve traffic operations and provide safe access for all users while planning for future needs in the area.
What problems exist at the intersection today?
Community members and traffic analysis have identified several challenges:
– Limited opportunities to safely make left turns from 8th Street East onto SR 121
– Continuous traffic flow on SR 121 that creates long delays
– Lack of pedestrian and bicycle facilities, which discourages walking and biking
– Driver uncertainty and risky maneuvers during peak commute periods
– Speeding and aggressive driving
What alternatives are being studied?
Two build alternatives are currently being evaluated:
– Roundabout Alternative
– Traffic Signal Alternative
A “no-build” option is also considered as part of the environmental review for comparison purposes.
Has a decision already been made?
A preferred alternative has not been selected. SCTCA is gathering technical data and community input before identifying a preferred alternative.
Why consider a roundabout?
SCTCA recognizes that roundabouts can feel unfamiliar or uncomfortable to some drivers, especially at first. This concern is being considered alongside safety and operational performance. Roundabouts are being evaluated because they can:
– Reduce vehicle speeds and calm traffic
– Reduce the severity of crashes
– Allow safer left turns and U-turns
– Allow for almost continuous flow in all directions with no mandatory stopping
– Reduce delay during most conditions
– Provide bicycle and pedestrian access
Will the roundabout really help create gaps to make a left turn at 8th or allow homeowners to get out of their driveways?
Yes, roundabouts are designed to keep traffic moving at slower, steady speeds, which often results in more frequent and predictable gaps in traffic. These gaps can make it easier for drivers to safely turn left onto 8th Street or exit their driveways, compared to traditional intersections where traffic can be more continuous or unpredictable.
Additionally, with the roundabout alternative residents located on the North side SR 121 can choose to make a right out of their driveway and easily make a U-turn, even with a truck and trailer, at the roundabout, rather than turning left across the highway.
Why consider a traffic signal?
A traffic signal is being studied because it can:
– Make left turns easier during red phases
– Provide controlled breaks in traffic flow
– Be familiar to drivers who are uncomfortable with roundabouts
– Provide bicycle and pedestrian access
Why would the signal alternative require widening SR 121?
A signal would likely require widening SR 121 to function safely and meet state standards.
To have this intersection operate at acceptable levels of service and reduce delay, the traffic study found that two through lanes plus dedicated turn lanes would be needed to accommodate traffic volumes.
These additional lanes would be created by widening SR 121 near the intersection so that lanes can transition from one lane to two lanes as vehicles approach the intersection, and then merge back to one lane beyond it. The required length of these lane transitions is based on roadway speed and Caltrans design standards.
Could the signal alternative encourage speeding or encourage passing?
During long green phases, drivers often speed, especially on straight sections of roadway, such as the location of the SR 116 / 8th Street East intersection. Having the two lanes could result in passing behavior within the multi-lane section of the roadway.
Some community members have raised concerns that additional lanes could encourage higher speeds or passing behavior. These concerns are being taken into consideration as part of the alternatives comparison and evaluation.
Why are bicycle and pedestrian facilities necessary if there are currently no bikes or pedestrians observed in the area?
Limited bicycle or pedestrian activity may reflect the lack of safe and accessible facilities. When infrastructure feels unsafe or incomplete, people are less likely to walk or bike. Some community members have shared that they avoid these modes in the area due to safety concerns.
State and Caltrans policies, including the Complete Streets policy, require roadway projects to consider the needs of all users, not just current motorists. This project is evaluating improvements that support safer crossings, future trail connections, and long‑term regional mobility.
The planned Sonoma–Schellville Trail is expected to link to the Bay Trail through the project area. Including bicycle and pedestrian facilities as part of this project is a cost‑effective way to support that future connection while construction is already underway.
Will landscaping be included?
Yes. Landscaping, which includes plantings and hardscape, is an important part of the project. During this phase of the project, the potential landscape areas are identified. The landscape design will take place during the final design phase. The landscaping will be:
– Low-maintenance
– Drought-tolerant
– Focus on native plants
– Maintain visibility for roadway users
Is this project being done because of a warehouse or Amazon?
No. The project is not tied to any specific private development or tenant. It is being advanced due to existing traffic challenges and long-term regional transportation needs. Any future development would be reviewed through a separate process.
Will this project help with emergency access and evacuation?
Emergency access and evacuation considerations are part of the evaluation process. Both alternatives are being reviewed to understand how they would perform during emergencies and high-demand situations. Both alternatives are also designed to accommodate large emergency vehicles and large trucks.
Will private property be affected?
As part of the environmental review process required under the California Environmental Quality Act (CEQA) and the National Environmental Policy Act (NEPA), the project team is currently evaluating potential environmental impacts, including those to private property, and developing alternatives.
Until the project is approved, agencies are not permitted to engage in negotiations regarding potential right-of-way needs, property acquisitions, or parcel-level impacts. This restriction is intended to ensure that the environmental process remains objective, unbiased, and free from any perception of pre-determination.
Any property boundaries, staging areas, or potential impact zones shown in project materials are conceptual and subject to change as the environmental studies continue.
Once the environmental document is completed and a preferred alternative is selected, the project will final right-of-way needs. At that point, direct outreach to affected property owners, appraisals, and negotiations can commence,, in accordance with state and federal requirements.
We are committed to transparency throughout the process and will provide updated information as it becomes available.
How will community feedback be used?
Community input is a critical part of the decision-making process. Feedback helps:
– Identify community priorities and concerns
– Clarify misconceptions
– Inform design refinements
– Weigh trade-offs between alternatives
All comments received are already becoming part of the project record, including reinforcing outreach commitments, clarifying driveway access, and explicitly studying speeding impacts.
Will there be more opportunities to participate?
Additional opportunities to provide feedback will be offered, and future outreach will include broader notification efforts and coordination with local groups and agencies.
How can I stay informed or submit comments?
– Visit the project website: https://scta.ca.gov/121-8th-street-east/
– Send comments by email to David Ripperda, Director of Projects & Programming, at David.Ripperda@scta.ca.gov.
– Attend future community meetings
– Provide comments on the draft environmental document, during the comment period.
What are the next steps?
Next steps for this phase of work include:
– Continuing technical and environmental analysis
– Refining the alternatives
– Identifying a preferred alternative
– Circulating a draft environmental document for public comment
The tentative schedule for the following phases is shown in the graphic below. All dates are tentative and dependent on environmental findings, funding, and approvals.
Project Timeline
A timeline for the project has been established to ensure key milestones stay on track:
Get Involved
Your input is critical in helping SCTCA to make effective improvements at this intersection that will benefit pedestrians, cyclists and motorists by increasing safety and multimodal access. Join the conversation and make your voice heard at an in-person public meeting.
