Methodologies for Traffic Impact Analysis in Moreno Valley

Methodologies for Traffic Impact Analysis in Moreno Valley

To ensure efficient traffic flow and maintain roadway performance in accordance with the policies established by the City of Moreno Valley’s General Plan, a thorough Level of Service (LOS) analysis is required. This analysis evaluates intersections and roadway segments, assessing their ability to accommodate existing and projected traffic volumes. The methodologies outlined below provide guidance on conducting these assessments effectively.

Intersection Analysis

The LOS analysis for intersections should adhere to the most recent edition of the Highway Capacity Manual (HCM) developed by the Transportation Research Board. The analysis should be conducted for both signalized and unsignalized intersections. Parameters not explicitly detailed in this guide should be determined using the professional judgment of the Engineer and remain subject to review by the City’s Transportation Engineering Division (TED). If there is any uncertainty in selecting the appropriate parameters, the Engineer should consult with TED during the report preparation phase.

Key parameters for the intersection analysis include:

• Saturation Flow Rate: The analysis should use a standard saturation flow rate of 1,900 passenger cars per hour per lane unless field measurements suggest otherwise.

• Heavy Vehicle Factor: The presence of heavy vehicles should be accounted for using count data. If necessary, a Passenger Car Equivalent (PCE) conversion can be applied to reflect heavy vehicle influence on traffic flow. Standard PCE values are:

  • Two-axle vehicles: 1.5 PCE

  • Three-axle vehicles: 2.0 PCE

  • Four or more axles: 3.0 PCE

• Grade Adjustment: The facility’s existing or proposed grade should be factored into the capacity calculations.

• Minimum Green Time: The minimum green time should be set at seven seconds per movement in areas with light pedestrian activity or per HCM guidelines in high pedestrian activity zones.

• Cycle Lengths: Optimal cycle lengths should be determined based on HCM recommendations, with a maximum of 120 seconds unless an exception is approved by TED.

• Peak Hour Factors: The analysis should incorporate peak hour factors derived from traffic count data. A future peak hour factor of 0.95 should be used.

• Software Requirements: All intersections must be evaluated using HCM-consistent software. In cases where closely spaced intersections exist, or queue spillback occurs, microsimulation software should be utilized to provide a system-wide analysis. This may include assessments of freeway facilities when applicable.

Mitigation Measures for Intersections

When evaluating potential mitigations, the following criteria should be used:

• Exclusive Left-Turn Lanes: Required if peak-hour left-turn volume exceeds 100 vehicles per hour.

• Dual Left-Turn Lanes: Considered when peak-hour left-turn volume surpasses 300 vehicles per hour.

• Protected Left-Turn Phasing: Recommended when the left-turn volume during peak hours exceeds 240 vehicles per hour, the opposing through movement consists of two or more lanes, or the posted speed limit is greater than 45 mph.

Roadway Segment Assessment

In certain cases, TED may require the evaluation of Average Daily Traffic (ADT) to determine overall roadway performance. This analysis is particularly relevant when:

• Intersection analyses are not the primary controlling factor.

• Roadway deletion or reclassification is being considered.

• Phased implementation of improvements is under review.

• A general planning assessment is required.

Table 1: Roadway Segment Capacities

Study Area Boundaries for LOS Assessment

At a minimum, the study area should include all intersections classified as “Collector” or higher where the proposed project adds 50 or more peak-hour trips. The study area should not exceed a five-mile radius unless justified by supporting evidence. Residential streets and intersections may require inclusion when the project is adjacent to residential areas. TED reserves the right to modify study area requirements based on local conditions.

Analysis Scenarios

To provide a comprehensive understanding of project impacts, the following scenarios should be analyzed:

1. Existing Traffic Conditions

   • Current traffic volumes should be collected to establish baseline conditions. Data should be collected within one year of the first draft submission unless TED grants an exception.

2. Project Completion Scenario

   • Future traffic conditions should be projected by applying an ambient growth rate provided by TED. Project-generated traffic should be added to evaluate potential impacts and necessary mitigations.

3. Project Phasing Analysis

   • If the project will be completed in phases, each phase’s impact should be evaluated separately. The assessment should include cumulative traffic from previous phases.

4. General Plan Buildout Analysis

   • For projects requiring General Plan Amendments, Zone Changes, or Specific Plans, a long-term analysis should be performed to determine if the Circulation Element is adequate or if additional mitigations are needed.

Project Phasing Approaches

For phased developments, the Engineer may employ one of the following methods:

1. Phase-Triggered Improvements

   • Identifies at which project phase improvements become necessary by comparing background conditions to projected conditions.

2. Opening Year Analysis

   • Evaluates each phase’s impact at its expected opening year.

3. Comprehensive Initial Evaluation

   • Conducts a single, comprehensive analysis covering all phases, with subsequent updates before implementing each phase.

TED must approve the selected approach before analysis begins.

Final Considerations

Proper coordination with TED is essential throughout the TIA process. Engineers should seek TED input before beginning analysis by submitting a TIA Scoping Agreement. This ensures agreement on key factors, including:

• Study area and scope

• Trip generation, distribution, and assignment

• VMT screening or assessment methodology

• Project-specific considerations such as pedestrian, bicycle, transit, and safety issues

For projects near city boundaries, engineers must also coordinate with adjacent jurisdictions and submit external agency comments to TED.

By adhering to these methodologies, the City of Moreno Valley ensures that development projects are evaluated rigorously, maintaining safe and efficient transportation infrastructure for all users

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