15.5.2 ATDM Analysis Process

The ATDM methodology builds on the reliability analysis described previously, which builds on a calibrated core freeway facility analysis described in Chapter 10 of the HCM 7th edition. Like the freeway reliability analysis process, the ATDM analysis process is timeintensive and includes extensive and repetitive calculations. Use an existing tool or software (FREEVAL-ATDM, Active Demand Management Capability Maturity Framework Tool, etc.) to streamline the analysis and minimize calculation errors. The following steps include the necessary analysis inputs and a description of when a calculation conducted by a tool or software can be automatically performed. Refer to
FHWA-HOP-18-072 Strengthening Linkages between Transportation Demand Management and Traffic Management
 for real-world examples of ATDM solutions.
  1. Limit Scenario List
     – ATDM strategies are often applied to a subset of scenarios to target a specific operational condition. If that is the case, the scenario list may be reduced to only include the appropriate scenarios that the ATDM strategy is expected to impact. For example, a freeway safety service patrol program may only be activated for scenarios in which a traffic incident has occurred, so only these scenarios can be analyzed with the ATDM strategy in place.
  2. Select Pool of ATDM Strategies
     – Select which ATDM strategies or plans to include in the evaluation and determine which strategies or plans can be applied to which scenarios.
  3. Convert ATDM Information to Operational Inputs
     – Convert the ATDM strategy into operational inputs, including the applicable AFs, incident duration adjustments, and number-oflane adjustments. The HCM 7th Edition, as of 2024, does not include default values for ATDM strategies, so the inputs are based on judgement or local data. For example, a freeway safety service patrol program might be shown locally to reduce incident duration for minor incidents by 30 percent, so all operational inputs that involve capacity adjustments over the duration of an incident are modified accordingly when evaluating scenarios with the strategy in place.
  4. Design ATDM Plans for the Facility and Assign to Scenarios
     – Identify which scenarios the ATDM strategies being analyzed apply to and determine the set of inputs. If multiple strategies are combined for a single scenario, multiply their respective AFs to produce a single factor for application to the scenario.
  5. Process ATDM Scenarios
     – Use a computational program or software (FREEVAL-ATDM, Active Demand Management Capability Maturity Framework Tool, etc.) to automatically evaluate each scenario by applying the HCM freeway capacity analysis core methodology.
  6. Compute Performance Measures
     – Use a computational program or software to calculate performance measures for the facility, with the ATDM strategies applied for each scenario.
  7. Process Before-and-After Comparison
     – Conduct a before-and-after comparison of ATDM strategy effectiveness by comparing the results of the reliability analysis with the results of the ATDM analysis. The focus of this comparison is on the travel time distribution before and after the implementation of the ATDM strategies.
  8. Validate Results
    – Compare ATDM analysis results with field data, results from other models, or expert judgement.
  9. Report Performance Measures
     – Report the facility’s reliability performance measures with the ATDM strategy or plan applied. Comparing these performance measures to those without an ATDM strategy in place could also allow for a B/C analysis based upon these performance measures, as described in
    Section 4
     of this chapter.