4.0 Analysis Methodology
This section outlines the methodologies to be used in a traffic impact analysis.
4.1 Intersection Analysis
The traffic impact analysis must include all intersections with more than 50 peak hour project trips. The City may, at its discretion, require analysis of additional intersections that do not meet the 50-trip threshold. Intersection analysis will be conducted using the latest Highway Capacity Manual (HCM) procedures. Additionally, HCM 2000 worksheets should be provided if requested by the City. It is recommended to use a software program capable of outputting multiple HCM methodologies for the analysis.
4.2 Roadway Link Analysis
Urban segments (i.e., segments on roadways that are generally signalized with spacing less than 2 miles) do not require segment analysis. Segment requirements are typically determined by analyzing lane requirements at intersections. However, segment analysis may be required at locations where the ultimate street cross sections are not constructed. Roadway link analysis can be conducted either based on daily traffic volumes or on peak hour volumes using vehicle-to-capacity ratios.
4.3 Freeway Analysis
Per SANBAG guidelines, freeway segments with more than 100 two-way peak hour project trips will require analysis. Freeway merge-diverge operations will require analysis if there are more than 50 peak hour project trips entering (or exiting) the freeway. These thresholds will be based on total vehicles (i.e., passenger cars and trucks if applicable), not on passenger car equivalents, because PCE factors differ for freeway mainline operations and freeway ramps. Freeway analyses should be conducted using the latest Highway Capacity Manual (HCM) procedures.
5.0 Study Area
Intersections with more than 50 peak hour project trips will require analysis. Additionally, roadway segments with more than 50 peak hour project trips may require analysis at locations where the ultimate street cross sections are not constructed. Freeway segments with more than 100 two-way project trips and merge-diverge areas with more than 50 peak hour project trips will also require analysis.
A meeting with the Department of Engineering is generally necessary to discuss the specific scope of the study prior to preparing the traffic study.
6.0 Analysis Scenarios
The TIA shall include the following analysis scenarios for roadway and intersection analysis:
- Existing Conditions: Determine the current baseline for the analysis, forming the basis for all future analysis scenarios. This will be based on traffic counts conducted for study intersections. Unless otherwise noted, a.m. and p.m. peak period counts will be conducted for all study intersections. Traffic counts older than one year at the time the scoping letter is submitted will not be acceptable unless approved by City Traffic Engineering staff.
- Opening Year Without Project Conditions: Based on applying a growth rate and/or adding traffic from reasonably foreseeable cumulative projects in the area, or by interpolating traffic volumes based on a traffic model.
- Opening Year With Project Conditions: Project traffic will be added to opening year without project traffic volumes to determine opening year with project traffic volumes.
- Opening Year With Project Conditions With Mitigation: If necessary.
- Future Build-out Year Without Project Conditions: Future year without project traffic volumes will be based on either a traffic model (SBTAM) or based on application of growth rates and addition of cumulative traffic volumes, determined in consultation with City staff. The future year will be 20 years from the project's opening day, rounded up to the nearest multiple of 5.
- Future Build-out Year With Project Conditions: Project traffic will be added to future year without project traffic volumes to determine future year with project traffic volumes.
- Future Build-out Year With Project Conditions With Mitigation: If necessary.
- For projects generating between 50 and 100 two-way peak hour trips, the analysis will only require Scenarios 1 through 4 as part of a focused traffic analysis.
- For projects forecasted to generate between 100 and 249 peak hour trips, future year traffic volumes may be based on either the application of growth rates and addition of traffic from cumulative projects or based on the San Bernardino Transportation Analysis Model (SBTAM) or another approved model.
- For projects forecasted to generate more than 250 peak hour trips, future year traffic volumes shall be based on the San Bernardino Transportation Analysis Model (SBTAM) or another approved model.
- For phased projects, the phases shall be identified and analyzed.
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