title
Receive a presentation on existing and future traffic conditions identified within the Suisun Valley Traffic Capacity Analysis study
body
Published Notice Required? Yes ____ No __X__
Public Hearing Required? Yes ____ No __X__
DEPARTMENTAL RECOMMENDATION:
Staff recommends that the Board of Supervisors receive a presentation on existing and future traffic conditions identified within the Suisun Valley Traffic Capacity Analysis study.
SUMMARY:
In December of 2023, the Board authorized the Director of Resource Management to contract for traffic engineering consultant services to study and analyze traffic in the Suisun Valley area. Recent development proposals in the last several years have generated public comment and concern regarding the potential for traffic to congest Suisun Valley with future development. The Department of Resource Management retained TJKM to perform traffic counts and prepare a capacity analysis which analyzes the existing traffic conditions along with 10-year projections for growth assumptions.
The Department has provided the attached Suisun Valley Traffic Capacity Analysis (Analysis) and will provide a presentation to the Board. In general, Suisun Valley area has enough capacity to handle the growth anticipated over the next decade; however, without improvements along the lowest segment of Suisun Valley Road there will be some future congestion on Saturdays.
FINANCIAL IMPACT:
The costs associated with preparing the agenda item are nominal and absorbed by the Department’s FY2025/26 Working Budget.
DISCUSSION:
In the 2008 General Plan, Suisun Valley received special zoning allowances for agricultural processing and wineries through a use-permit process. In the last decade, the Department has seen an increase in use-permit applications for wineries, agritourism centers and events that require California Environmental Quality Act (CEQA) review, public outreach and/or comment. Over the past decade, the County completed several federally funded road improvement projects in Suisun Valley. These projects improved road design and safety, added pedestrian and bicycle facilities, and helped ensure that traffic flow kept pace with development.
In the last five years, some of the larger permits have generated comments and concerns regarding potential traffic congestion related to this growth. The consultant, TJKM, reviewed existing traffic counts and requested further counts on adjacent roads, and across sample time-spectrums, to provide a clear picture of traffic conditions throughout the year. The Analysis focused primarily on Suisun Valley Road, from Rockville Road south to the Solano Community College, as the traffic spine that most traffic flows through. Traffic engineers measure roadway performance using “Level of Service (LOS),” which ranges from A (free-flowing traffic) to F (heavy congestion and stop-and-go conditions) as outlined below:
Level of Service:
A - Free-flow traffic, high speed, high maneuverability
B - Reasonably free flow, slight restriction in maneuverability
C - Stable flow, speed and maneuverability closely restricted
D - Approaching unstable flow, low speed and freedom, minor incidents cause queues
E - Unstable flow, at or near capacity, significant delays
F - Forced or breakdown flow, traffic demand exceeds capacity, stop-and-go traffic or breakdown flow, traffic demand exceeds capacity, stop-and-go traffic
In the Analysis attached (Attachment A, Tables 4 & 5), the road network shows a LOS A under normal existing conditions. While the road network may have occasional LOS delays, such as Friday afternoons before holidays, the average of the days over time show good performance. Improvements to Interstate 80 have also likely improved the outcomes in Suisun Valley as less traffic is induced to travel from Napa County through Suisun Valley.
The Analysis also looked ahead 10 years, assuming the wineries and agritourism uses already planned in the Valley are built. Under that scenario, traffic would continue to flow well during normal weekdays. However, during peak harvest Saturdays, when visitor activity is highest, the southern portion of Suisun Valley Road (Segment A between Rockville Road and Solano Community College) is expected to experience some congestion and delays.
Importantly, the Department has secured federal funding through the Priority Conservation Area program to improve the roadway design and safety of Segment A. The project will widen lanes to standard width, add shoulders, and install a sidewalk connection between Rockville Corners and Solano Community College. These improvements are expected to improve traffic flow and reduce delays during busy periods, helping to ease projected congestion while enhancing overall safety.
Through the scoping process for future roadway improvement projects and buildout conditions, the Department sought input from the Solano Transportation Authority’s Bicycle Advisory Committee and Pedestrian Advisory Committee, the Solano County Farm Bureau, and the Metropolitan Transportation Commission. The Department also revisited public comments on Suisun Valley traffic from the last few public hearings on various developments. The comments were primarily focused to ensuring adequate on-site parking, limiting regional congestion within the Suisun Valley corridor, and maintaining safety at the intersection of Suisun Valley Road and Rockville Road.
The Analysis confirms that Suisun Valley Road operates at LOS A today and will continue to perform well during normal weekday conditions at 10-year buildout. Overall, future traffic conditions are projected to be very similar to existing conditions. The only scenario where there may be strain is during peak Saturday harvest season near the I-80 gateway, where short-duration congestion occurs. That peak-period strain is typical of successful agritourism regions and is geographically limited to the southern segment. Outside of those peak hours, the corridor maintains good operating conditions and has sufficient capacity to support the planned zoning and future development of the area.
ALTERNATIVES:
The Board could choose not to receive the presentation; however, this is not recommended as it gives the Board the opportunity to receive information that has been requested through numerous public comment processes.
OTHER AGENCY INVOLVEMENT:
The Department of Resource Management received information from the Solano Transportation Authority for the traffic data and from the City of Fairfield for transit/student traffic near Solano Community College.
CAO RECOMMENDATION:
APPROVE DEPARTMENTAL RECOMMENDATION