Level of Service (LOS) Analysis Methodology and Requirements for TIAs in the City of Calimesa

Level of Service (LOS) Analysis Methodologies

To ensure consistency with the City of Calimesa’s General Plan policies, LOS analysis is required for Transportation Impact Analyses (TIAs). The analysis must follow the methodologies established in the most recent edition of the Highway Capacity Manual (HCM) developed by the Transportation Research Board. This applies to both signalized and unsignalized intersections.

Intersection Analysis Parameters

Intersection evaluations must be completed using HCM-consistent software. The following technical parameters and assumptions should be incorporated into the analysis:

• Saturation Flow Rate: Use 1,900 passenger cars per hour per lane, unless site-specific field measurements are available.

• Heavy Vehicle Factor: This should be based on observed count data or values provided by the City Traffic Engineer. Analysts may either apply a Passenger Car Equivalent (PCE) factor directly to the traffic volume or incorporate it into the capacity calculation per HCM guidelines.

• Grade: Utilize actual or proposed grades for the evaluated intersections.

• Signal Timings: Green time, cycle lengths, and lost time should be based on current signal timing sheets (provided by the City or collected in the field). If unavailable, analysts should apply HCM default recommendations.

• Peak Hour Factor (PHF): Derive from count data; for future conditions, assume a PHF of 0.95.

• Closely-Spaced Intersections: If traffic queues affect upstream or downstream intersections, use microsimulation software to evaluate the network as a system. This may include freeway ramps or other corridor segments as necessary.

Mitigation Guidance for Intersections

When intersection mitigation is needed, the following design considerations are recommended:

• Exclusive Left-Turn Lanes: Consider if left-turn volumes exceed 100 vehicles during the peak hour.

• Dual Left-Turn Lanes: Consider for intersections with peak hour left-turn volumes exceeding 300 vehicles.

• Protected Left-Turn Phasing: Should be analyzed when peak hour left-turn volume is greater than 240 vehicles.

Roadway Segment Analysis

In some cases, the City Traffic Engineer may request an evaluation of roadway segments in addition to intersections. Segment capacities should reflect City standards. In the absence of locally defined capacities, use values consistent with HCM guidance.

LOS Study Area Definition

As a general rule, the LOS analysis should include all intersections involving a “Collector” street or higher functional classification where the proposed project is anticipated to add 50 or more trips during the peak hour. Typically, the analysis area will extend up to a 5-mile radius from the project site. However, based on project-specific factors or regional network characteristics, the City Traffic Engineer may adjust the study area.

Required Analysis Scenarios

Intersection capacity analyses must evaluate the following five scenarios:

1. Existing Conditions – Current traffic volumes and roadway configurations.

2. Background Conditions – Opening year traffic volumes, including trips from already approved (but not yet constructed) developments. If few approved projects exist, a background growth rate may be applied instead.

3. Background Plus Project Conditions – Background conditions with the addition of traffic generated by the proposed project.

4. Cumulative No Project Conditions – Long-range conditions (typically aligned with the RIVTAM/RIVCOM model forecast horizon) that include all known cumulative developments and regional growth.

5. Cumulative Plus Project Conditions – Cumulative No Project conditions plus project-generated traffic.

Considerations for Phased Projects

For developments constructed in phases, traffic impacts can be evaluated using one of the following methods:

• Trigger-Based Analysis: Identify which project phase requires specific improvements by comparing Background Conditions to Background Plus Project Conditions.

• Phase-by-Phase Analysis: Conduct separate assessments for each phase's opening year.

• Full Build-Out Evaluation: Evaluate the full build-out initially, followed by focused updates for each new phase as it is implemented.

Consultation with the City Traffic Engineer is required to determine the most suitable approach based on project scale and timing. Generally, the trigger-based method is preferred for phased projects to ensure improvements are timed appropriately.

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