Level of Service Assessment for General Plan Consistency
3.1 Scope of Transportation Impact Study
The scope of a transportation impact study should ensure that potential impacts are thoroughly analyzed and mitigated across various facilities and future scenarios. Our recommendations for the study area and scenarios are outlined below.
3.1.2 Study Area Boundaries for LOS Assessment
The study area should include all intersections where the proposed project will add 50 or more trips during any peak hour and adjacent roadway segments if directed by the County. Key study facilities within this area should be analyzed to identify impacts on capacity and Level of Service (LOS). These facilities should be listed in the scoping form for review and approval by the Traffic Division.
At a minimum, the following subjects/locations should be studied:
- Site access driveways
- On-site circulation
- Adjacent roadways (if requested by County staff)
- Intersections in the immediate vicinity of the project
- Pedestrian and bicycle circulation
- Consistency with County Plans and Policies
- Transit accessibility (bus and light commuter rail)
- Any intersection where the project will add 50 or more peak hour trips
3.1.3 Study Scenarios for LOS Assessment
The following study scenarios should be included for intersection capacity analysis:
- Existing Conditions
- Background Conditions: Opening Year Conditions with ambient growth and traffic from approved projects
- Background Plus Project Conditions: Background conditions plus traffic from the proposed project
- Cumulative No Project Conditions: Ambient growth to the Cumulative Horizon (typically coinciding with the forecast horizon of the SBTAM travel demand forecasting model) plus traffic from approved and pending projects in the area
- Cumulative Plus Project Conditions: Cumulative No Project Conditions plus traffic from the proposed project
The purpose of Background Condition analyses is to document the potential near-term impacts of the project on the County’s transportation facilities. However, if the project opening year is more than five years beyond the Existing Conditions assessment, then an Existing Plus Project scenario should be analyzed as an additional scenario.
Phased projects can be evaluated in three ways:
- Identify which phase of a project triggers an impact based on the comparison of Background Conditions to Background Plus Project Conditions.
- Provide a phased assessment looking at opening years of each phase.
- For large phased projects, evaluate the project as a whole initially, with subsequent traffic studies completed for each proposed phase implementation to ensure improvements are implemented when needed.
The County should be consulted to identify the most appropriate approach for a proposed project with phasing, ensuring that infrastructure is delivered concurrently with development.
Recommendations for developing Ambient Traffic and Cumulative Traffic are provided in the next section of this document.
Our Services are available throughout San Bernardino including citiesGrand Terrace, Hesperia with Zipcodes 92313, 92340