1.2.3 Level of Detail

The level of detail is different than the PDS and describes the detail necessary to complete an analysis. Analysis tools are often categorized into varying levels of detail. The necessary level of detail for an analysis, as well as project scope and complexity, often influence tool selection. Level of detail is divided into three categories:
  • Sketch-Level or Macroscopic
    • Sketch-level analysis tools may use less input and detail. This type of tool may be suitable for projects that have limited resources (data, budget, expertise, personnel, time, etc.), or projects that do not use high levels of detail. An example of a tool in this category is Capacity Analysis for Planning of Junctions (CAP-X).
    • Macroscopic tools, such as travel demand model (TDM) outputs, may be used for complex projects that have regional/subregional impacts. Analyses that use these types of tools often involve more resources than typical sketch-level tools. Coordination with TxDOT’s Transportation Planning and Programming (TPP) Division or the local Metropolitan Planning Organization (MPO) may be necessary when travel demand outputs are used for a project.
  • HCM-Based (Mesoscopic)
    • Analysis tools at this level involve a medium amount of input and detail or are HCM-based.
    • An example of this type of tool is the Highway Capacity Software (HCS).
  • Microsimulation (Microscopic)
    • Analysis tools at this level likely involve the most input and detail. They are suitable for projects that are complex or use detailed operational analysis. Examples of these tools include Verkehr in Staedten Simulation (Vissim), Corridor Simulation (CORSIM), and SimTraffic..
Like the PDS, the level of detail can also be considered multi-resolution if the analysis includes a combination of Sketch-Level or Macroscopic, HCM-Based (Mesoscopic), and Microsimulation (Microscopic) tools. Use the PDS and level of detail to guide the selection of appropriate tools for analysis. Determination of level of detail (including multi-resolution modeling) for scoping is based on a variety of factors; work with the TxDOT project manager, TxDOT’s Design Division (DES), and/or TPP to determine which level of detail fits for the project. See for an
example
of how to fill out this section.
Analysis tools typically used in safety-related projects include TxDOT’s Safety Scoring Tool (SST), Safety Performance of Intersection Control Evaluation (SPICE), HSM for Rural Multilane, HSM for Urban/Suburban Arterials, HSM for Rural Two-Lane Roads, Enhanced Interchange Safety Analysis Tool (ISATe), Highway Safety Software (HSS), and Interactive Highway Safety Design Model (IHSDM). These tools are often used to achieve results varying in level of detail.