16.4.1 Existing Conditions

The existing field conditions within the study area are analyzed as a baseline to compare future conditions. By analyzing existing conditions, the impact a development has on the roadway system from a traffic operations standpoint can be measured. The existing conditions analysis also serves as a calibration step for the performance assumptions within the analysis procedure (e.g., saturation flow rate, gap acceptance) that can vary by geographical area and user demographics. The results of the existing conditions analysis are compared to the field observations so that the preparing engineer and reviewers can be confident that the model is valid for use in projecting future conditions.
  • Peak Hour Counts
    • If the appropriate data is called for, counts at major intersections near the proposed project driveways are conducted to obtain AM and PM peak hour traffic volumes. These volumes are typically shown in an
      Existing Traffic Volumes exhibit.
    • Typical analysis hours are the AM and PM peak hours. Other analysis hours can be evaluated as needed (e.g., midday peak, Saturday peak, or school peak), depending on the project site and adjacent land use. These alternate analysis hours are typically developed during the preliminary scoping stage.
    • If there are multiple intersections being counted, the hour with the highest cumulative total volumes across all intersections typically serves as the analysis hour.
    • Counts can be collected in a variety of ways with the most common forms being field TMCs, counts from ITS devices, and count data for other transportation modes including bicycles, pedestrians, transit, etc. It is recommended that raw count data be provided in the appendix of the report.
  • Field Observations
    • A field visit helps explain the physical and operational conditions of the study area. Common observations include existing geometry, traffic control, queuing, delays, and pedestrian/bike activity.
    • It is recommended that a field visit take place as part of a TIA and observations be documented in the report.
    • For safety considerations in a TIA, it is recommended that intersection sight distance is analyzed and TxDOT’s right-turn warrant thresholds are evaluated.
  • Traffic Signal Timings
    • Timings are typically requested for any signalized intersections to be studied within the study area from TxDOT. These timings are used to model the existing conditions.
  • Traffic Analysis Output
    • Existing traffic counts are used for volume inputs, heavy vehicle data, non-motorist activity, and other related characteristics of the surrounding roadway network.
    • The existing LOS for any significantly impacted intersections is typically displayed using the latest HCM analysis methodology. For signalized intersections, each approach and the overall intersection are analyzed. For stop-controlled intersections, each stop-controlled approach is analyzed by the approach. Leftturning movements of non-stop controlled approaches are analyzed by movement
    • Multimodal (pedestrian/bicycle) activity within the project vicinity is typically addressed. Multimodal improvements such as sidewalks and crosswalks are also typically evaluated for the project