3.3. Intersection Operational Analysis
The intersection operational analysis assesses the impact of a proposed development project on the level of service (LOS) and exclusive turn-lane vehicle queuing near the project site. This involves comparing the LOS and turn-lane queuing with and without the added traffic from the project against the City’s minimum LOS standards to identify any negative operational effects.
3.3.1. Study Area
The study area for the LOS analysis should encompass all project driveways and the nearest signalized intersections adjacent to the site. Additional locations may be necessary based on the project's specific characteristics, determined in consultation with the Department of Transportation (DOT) during the scoping/MOU process. The analysis must include existing exclusive left-turn lanes and any proposed lanes at project driveways, while exclusive right-turn lanes may also be included as needed. Operational analyses are typically not required for unsignalized intersections, although traffic signal warrant analyses may be necessary. The analysis scope should not end at city boundaries, requiring coordination with other local agencies for potential impacts.
3.3.2. Data Collection and Study Periods
LOS and turn-lane queuing analyses should generally occur during weekday morning and evening peak hours, with traffic volumes collected in 15-minute intervals during these periods (7:00 AM to 9:00 AM and 4:00 PM to 6:00 PM). Traffic counts should be conducted on mid-week days when local schools are in session, under good weather, and not during holidays. Counts taken under different conditions require DOT approval. Recent traffic data (less than two years old) is preferred, while older counts may be acceptable if supported by significant changes in local conditions. Existing use trip credits should also be factored into counts if applicable.
3.3.3. Project Trip Generation and Adjustments
The vehicle trip generation forecast should use data from the current ITE Trip Generation Manual, following recommended practices. For some land uses, empirical data may be utilized, especially when ITE data is insufficient. The trip generation forecast must include weekday daily, AM peak hour, and PM peak hour trips, summarized in a table format identifying the data source and any applicable adjustments, submitted to DOT during the scoping/MOU process. Potential adjustments include:
- Existing Use Credits: For sites with existing land uses to be demolished.
- Internal Capture Adjustments: For mixed-use developments accounting for internal trips.
- Transit Adjustments: For projects near transit services.
- Pass-by Adjustments: For trips attracted from passing traffic.
If TDM measures are needed to reduce vehicle trips, their credits must be discussed with DOT.
3.3.4. Project Trip Distribution and Assignment
The project trip distribution should indicate the inbound and outbound trip percentages at each study intersection based on existing travel patterns and major corridors, to be submitted to DOT. A trip assignment figure illustrating peak hour net new project trips at study intersections should also be prepared.
3.3.5. Analysis Scenarios
The intersection analysis should evaluate LOS and turn-lane queuing under various scenarios:
- Existing Conditions: Based on collected volume data.
- Existing with Project Conditions: Existing data plus new project traffic.
- Future (Project Build-Out) Baseline Conditions: Conditions expected when the project is fully constructed.
- Future (Project Build-Out) With Project Conditions: Future baseline plus project traffic.
- Future Cumulative With Project Conditions: General Plan conditions plus project traffic.
3.3.6. Future Traffic Condition Forecasting
Forecasts for future traffic conditions must include existing volume increases and traffic from known nearby developments, based on sources like SCAG's regional program. A list of related projects should be compiled to assess their cumulative impact.
3.3.7. Methodology and Analysis Parameters
LOS and queuing calculations should use the HCM methodology and Synchro software. Key parameters include:
- Saturation Flow Rates for different lane types.
- Peak Hour Factor (PHF) determined from field data.
- Collection of pedestrian, bicycle, and vehicle volumes during peak traffic counts.
Light rail crossings affecting roadway operations should be included in the analysis model. In cases of network oversaturation or closely spaced intersections, micro-simulation analyses may be necessary.
3.3.8. Assessment Criteria
The minimum acceptable LOS is D, with E in Transit Oriented Districts (TOD). Any deterioration beyond these standards due to project traffic requires corrective measures. Excessive turn-lane queuing that interferes with traffic flow also necessitates solutions.
3.3.9. Improvements
Improvement measures should enhance the existing street system's efficiency, focusing on non-vehicular travel modes. Options include signal upgrades and synchronization, with the City’s Street Design Guide as a reference for potential enhancements aligned with the General Plan's complete streets policy.
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