15.5 Transportation Demand Management (TDM)

According to the FHWA, TDM is a group of strategies designed to maximize traveler choices. These strategies are aimed at improving travel reliability. They affect an entire system and analysis periods, when there is an overall change in demand, most commonly when there is a reduction in demand. Although TDM is a set of strategies, it is most helpful to focus on individual strategies within the set that can be integrated into existing activities within the State or regional planning process.
The traffic analysis for the effectiveness of TDM improvements is typically based on objectives and rely on performance measures. Example performance measures that may be used for TDM analysis are shown below:
  • Percentage of commute trips taken by a non-single-occupancy vehicle (SOV) mode;
  • Number of vanpool/carpool participants;
  • Percentage of residents within proximity of a park and ride facility;
  • Percentage of residents within proximity of a transit stop;
  • Number of centerline miles for active transportation facilities;
  • Availability of real-time traveler information;
  • Availability of last mile connections;
  • Availability of micro-mobility rides; and
  • Travel time data-sharing
Below are general TDM strategies that can be implemented or analyzed:
  • Multimodal
    – Using different modes of transportation (walk, bicycle, transit, personal vehicle) to complete a trip without increasing the number of vehicles.
  • Ridesharing
    – Reducing the number of SOV trips to reduce the number of vehicles on the road.
  • Flexible Work Schedule
     – Teleworking or working flexible hours to take an alternate route or alternate departure time.
  • Land Use
     – Providing compact land uses that reduce the distances between origins and destinations for live, work, and play. Supporting more travel choices and making transit, walking, and cycling more practical.

15.5.1 Active Transportation and Demand Management (ATDM) Strategies

FHWA defines ATDM as the dynamic movement, control, and influence of travel demand, traffic demand, and traffic flow on transportation facilities. ATDM is part of the broader concept of TSMO, with a deeper focus on the active management principle of TSMO and combining ATDM strategies. The ATDM analysis methodology in the 7th Edition of the HCM distinguishes between five principal categories of strategies that may affect facility operations:
  • Demand Management Strategies
     – These strategies alter the entire system of segments and analyses when they are used in the event of an increase or decrease in demand.
  • Weather Management Strategies
     – These strategies only impact performance during analysis periods when a severe weather event affects the facility and apply equally to all segments. For example, weather-related driver information, snow removal, flood closures, etc.
  • Incident Management Strategies
     – These strategies only impact the performance of segments and analysis periods when an incident occurs. For example, freeway service patrol, driver information, dynamic lane assignment, etc.
  • Work Zone Management Strategies
     – These strategies only impact the performance of segments and analysis periods when a work zone is present. For example, end-of-queue warning system, dynamic merge control, etc.
  • Special Segment-Specific Strategies
    – These are the strategies not covered in the previous categories. These strategies impact the performance of specific target segments. For example, ramp metering, hard shoulder running, etc

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.