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TIA Requirements

TIA Scope

The scope of the Traffic Impact Analysis shall be based on the peak hours trips projected to be generated by the proposed development, as set for in the following table. The consultant preparing the study must meet with City staff to discuss the scope and requirements of the study.


Nonresidential Peak Hour Trips Residential Peak
Hour Trips
TIA Scope
100 or less  100 or less  *Trip Generation Worksheet Required. No TIA Required. 
101-300  101-300  The frontage of the property, all access points (including common access), and all intersections within a 1/4 to 1/2 mile radius of the proposed development. 
301-500  301-500  The frontage of the property, all access points (including common access), and all intersections within a 1/2 to 1 mile radius of the proposed development. 
501 or more  501 or more  The frontage of the property, all access points (including common access), and all intersections within a 1 mile radius of the proposed development. 

* If no TIA is required then intersection sight triangles to be submitted for all intersections.


Trip Generation

Trip generation shall be based on the specific site use and calculated using the latest edition of the Institute of Transportation Engineers (ITE) Trip Generation Manual. If specific land use is not known Trip Generation shall be based on max build out for the most stringent land use based on current or proposed zoning.


Trip Distribution

Trip distribution shall be based on current peak hour traffic movements and may be adjusted to reflect future, financially assured, roadway improvements.


Study Time Frames

The analysis should include the following conditions:


  • Existing traffic volumes and roadway conditions
  • Existing traffic volumes and roadway conditions plus projected site generated traffic
  • Existing traffic volumes with improved roadway conditions plus projected site generated traffic (when specified by City of McAllen staff)

The analysis should be performed for a typical week day unless specified by City of McAllen staff. The analysis shall include both the AM and PM peak hours, 24-hour generations, and special times or days of the week dependant of the land use’s peak traffic generating time periods as determined from the Trip Generation Manual.


Access Analysis

Intersection needs at all the development’s access points shall be determined. Spacing of the access points shall be determined both by the City of McAllen’s ‘Access Management Policy’ and the operational analysis. This operational evaluation shall include on-site circulation as it may affect access, on-site and off-site turn lanes, required storage, potential for signalization, review of sight distance and other intersection safety aspects. Site distance triangles shall be shown on the site plan/ plat and calculated using the latest addition of the American Association of State Highway and Transportation Officials, “A Policy on Geometric Design of Highways and Streets” (Green Book). Usage of common access driveways is encouraged to reduce the total number of connections to the roadway network.


Level of Service Evaluation

Both roadway capacity and intersection capacity shall be evaluated as part of the level of service analysis. The level of service evaluation for roadways shall be based on the latest edition of The Highway Capacity Manual (HCM). The volume to capacity ratio (v/c) is an important indicator of roadway capacity and shall be included as part of the level of service tables. Intersection level of service shall be calculated using the latest Intersection Capacity Utilization (ICU) methodologies. The intersection level of service tables shall include volume to capacity ratios (v/c) as well as volume to saturated flow ratios (v/s).


Recomendations

Recommendations shall be put forth to preserve existing roadway network operations. The recommendation may include the following incremental improvements:


  • Left turn bays
  • Increased storage lanes
  • Right turn declaration lanes
  • Conversion of Two-way Stop control to All-way Stop control, if warrants are met and staff approves
  • Conversion of All-way Stop control to roundabout or traffic signal, if warrants are met and staff approves
  • The installation of a traffic signal, if warrants are met and staff approves
  • Improved signal timing or phasing
  • Roadway expansion or extension
  • Various access management measures to improve overall circulation and/or safety

Any suggested changes to signal timing must evaluate the effects to the entire network of affected signals and not just the signalized intersections in question. Recommendations put forth to expand or extend roadways shall conform to the Foresight McAllen comprehensive plan.



Mitigation

Mitigation may be required based on the TIA recommendations or to account for the cumulative effect of development on the roadway network. In the case of cumulative mitigation, fees may be charged proportionately to fund future roadway improvements.


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