Intersection Evaluation for the Project in San Bernardino

3.4.1 Analysis Methodology Intersection analyses should be conducted using the latest version of the Transportation Research Board's Highway Capacity Manual (HCM), currently the HCM 6th Edition. This methodology assigns a Level of Service (LOS) grade to an intersection based on the estimated delay at that intersection. The analysis should use the following assumptions:

• Existing signal timing for Existing Conditions; optimized signal timing for non-coordinated intersections for all other analysis scenarios.
• For coordinated intersections, obtain the existing coordination timing plan from the responsible agency.
• Assume four (4) seconds of lost time per critical phase if signal timing data is not available.
• Use field-collected heavy vehicle factor if available; otherwise, assume 2%.
• Use field-collected peak hour factor (PHF) for existing and background conditions analyses; for cumulative assessment, assume 0.95.

Saturation flow rates should be based on actual field measurements of particular intersections if possible and approved by the Traffic Division. Otherwise, the following saturation flow rates should be used, consistent with the SBCTA CMP:

• For Existing and Background scenarios:

  • 1,800 vehicles per hour green per lane (vphgpl) for exclusive thru and exclusive right turn lanes
  • 1,700 vphgpl for exclusive left turn lanes
  • 1,600 vphgpl for exclusive dual left turn lanes
  • 1,500 vphgpl for exclusive triple left turn lanes

• For the Cumulative and General Plan Build-Out scenarios:

  • 1,900 vphgpl for exclusive thru and exclusive right turn lanes
  • 1,800 vphgpl for exclusive double right turn lanes
  • 1,800 vphgpl for exclusive left turn lanes
  • 1,700 vphgpl for exclusive dual left turn lanes
  • 1,600 vphgpl for exclusive triple left turn lanes

3.4.2 Signalized Intersection General Plan Consistency Requirements To ensure consistency with the acceptable LOS for the Desert, Valley, and Mountain regions as outlined in the General Plan, the following criteria should be considered for signalized intersections in a traffic study:

• Any signalized study intersection in the Valley or Mountain regions operating at LOS D or better without project traffic, where the addition of project traffic degrades it to LOS E or F, should identify improvements to achieve LOS D or better.
• Any signalized study intersection in the Desert region operating at LOS C or better without project traffic, where the addition of project traffic degrades it to LOS D, E, or F, should identify improvements to achieve LOS C.
• Any signalized study intersection in the Valley or Mountain regions operating at LOS E or F without project traffic, where the project increases delay by 5.0 or more seconds, should identify improvements to offset the increase in delay.
• Any signalized study intersection in the Desert region operating at LOS D, E, or F without project traffic, where the project increases delay by 5.0 or more seconds, should identify improvements to offset the increase in delay.

3.4.3 Unsignalized Intersection General Plan Consistency Requirements In line with the acceptable LOS for the Desert, Valley, and Mountain regions as described in the General Plan, the following criteria should be applied to unsignalized intersections when identifying operational deficiencies:

An operational improvement is required if either condition a) or both conditions b) and c) occur:

a) The addition of project-related traffic causes the intersection to degrade from LOS D or better to LOS E or worse in the Valley and Mountain regions or from LOS C or better to LOS D or worse in the Desert region.

OR

b) The project adds 5.0 seconds or more of delay to an intersection already projected to operate without project traffic at LOS E or F in the Valley and Mountain regions or at LOS D, E, or F in the Desert region.

AND

c) One or both of the following conditions are met:

1. The project adds ten (10) or more trips to any minor street approach.
2. The intersection meets the peak hour traffic signal warrant after the addition of project traffic.

If these conditions are met, improvements should aim to achieve the following:

• In the Valley and Mountain regions, improvements should achieve LOS D or better for condition a) or restore pre-project LOS and delay for condition b).
• In the Desert region, improvements should achieve LOS C or better for condition a) or restore pre-project LOS and delay for condition b).

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