9.3.2 Analysis Tools

HCM based methods are used for segment analysis when a TDM is unavailable or unsuitable for the project. Several types of HCM-based (mesoscopic) software can be used to analyze segments. As with all HCM-based (mesoscopic) tools, they are deterministic and will output the same results given the same inputs. HCS is the recommended software when conducting segment analysis, but other HCM-based (mesoscopic) software can be used if HCS is unavailable or does not include analysis of the facility type in question. Synchro is recommended for the analysis of arterial roadways and other segments whose LOS is mainly based on intersection delay. Detailed illustrations of inputs and outputs of HCS can be found in
Appendix J, Section 2 – HCS Data Inputs and Outputs by Segment Type
. For detailed guidance on inputs and outputs of other HCM-based (mesoscopic) tools, refer to each tool’s user guide and/or software. Several available software and analysis capabilities include:
  • HCS;
    • Facility capabilities
      • Basic freeways
      • Basic multi-lane highways
      • Weaving segments of freeways
      • Merge and diverge segments of freeways
      • Two-lane highways
      • Arterial facilities
  • FREEVAL;
    • Facility capabilities
      • Basic freeways
      • Basic multi-lane highways
      • Weaving segments of freeways
      • Merge and diverge segments of freeways
      • Two-lane highways
    • Other capabilities
      • Work zone impact assessment
      • Managed lanes analysis
      • Travel time reliability analysis
  • HCM-CALC; and
    • Facility capabilities
      • Basic freeways
      • Basic multi-lane highways
      • Weaving segments of freeways
      • Merge and diverge segments of freeways
      • Two-lane highways
  • Synchro
    • Facility capabilities
      • Segments with signalized intersections
      • Segments with roundabouts
      • Segments with all-way stop-control or two-way stop-control
While some of the default values in the software listed above can be used to conduct analysis of segments, it is recommended that four characteristic inputs to these tools represent actual conditions in the field:
  1. Segment length
  2. Free flow speed
  3. Number of lanes
  4. Flow rates
Field data for other default values are collected and inputted based on engineering judgement.

9.3.2.1 Texas A&M Transportation Institute (TTI) Procedures

TTI has developed procedures for analyzing one-way and two-way frontage roads. Frontage roads operate similarly to arterials since they are corridors with signalized or unsignalized intersections. However, frontage roads also have ramp connections to and from freeways and driveways on only one side. TTI used HCM’s urban and suburban arterial LOS analysis as a base model for analyzing frontage roads and made modifications to the methodology to account for ramp interactions and driveways to develop a seven-step process for evaluating frontage road operations. The steps can be repeated to analyze both sides of a two-way frontage road. It is recommended to follow the seven-step process, substituting the latest HCM methodologies where relevant. See for a flowchart that provides an overview of TTI’s seven-step process for frontage road analysis. A guide with
examples
 is included in
Appendix J, Section 1 – TTI Frontage Road Analysis Steps and Examples
.