Office of Operations Active Transportation and Demand Management

Guide for Highway Capacity and Operations Analysis of Active Transportation and Demand Management Strategies

1. Introduction

ATDM is the dynamic management, control, and influence of travel demand, traffic demand, and traffic flow of transportation facilities. Through the use of available tools and assets, traffic flow is managed and traveler behavior is influenced in real-time to achieve operational objectives, such as preventing or delaying breakdown conditions, improving safety, promoting sustainable travel modes, reducing emissions, or maximizing system efficiency. Under an ATDM approach, the transportation system is continuously monitored. Using archived data and/or predictive methods, actions are performed in real-time to achieve or maintain system performance. ATDM is a transportation-specific application of Active Management. Active Management is the fundamental concept of taking a dynamic approach to a performance-based process which is routinely used in many other industry sectors such electrical utilities, telecommunications, information technology network management. Figure 1 depicts the four key steps in the active management cycle.

Figure 1: The Active Management Cycle

Figure 1 is a graphic showing a circular cycle with Monitor System leading into Assess System Performance, leading into Evaluate and Recommend Dynamic Actions, leading into Implement Dynamic Actions, which leads back into Monitor System.

Source: FHWA.

This Guide focuses on the analysis of active traffic management, and to a lesser degree, active demand management approaches. Additional information and resources on ATDM and the FHWA ATDM program activities can be found on the ATDM web site.

1.1 Purpose

This Guide provides HCM-related methodologies and measures of effectiveness for evaluating the impacts of ATDM strategies on highway and street system demand, capacity, and performance. The Guide is designed to assist engineers and planners in evaluating the traffic operations effects of various ATDM strategies on a specific facility and to determine which combination of strategies best achieves a desired operational goal for a facility. As such, the Guide will be valuable for the planning, prioritization, and programming of ATDM investments.

Organization

This Guide is organized as follows:

  • Chapter 1: Introduction: describes the scope, purpose, limitations, and organization of the Guide.
  • Chapter 2: Measures of Effectiveness – presents recommended measures that build on traditional HCM measures for assessing the effectiveness of ATDM measures.
  • Chapter 3: ATDM Strategies Toolbox – provides an overview of active transportation and demand management measures.
  • Chapter 4: Overview of ATDM Analysis Methodology – provides an overview of the ATDM Analysis methodology.
  • Chapter 5: Methodology – presents the methodology in step-by-step detail.
  • Chapter 6: Example Application – provides a worked example application of the methodology.
  • Chapter 7: Use of Alternative Tools – provides brief guidance on the use of other traffic operations analysis tools besides the HCM to evaluate ATDM investments.

The Appendices provide additional background on the development of demand, free-flow speed, and capacity adjustment factors for weather, incidents, and work zones.

Scope and Limitations

The methodology described here is designed to be applied to any traffic control, toll, or capacity improvement that affects the demand, capacity, speed, and reliability of a highway facility. The methodology should be viewed as an initial, foundational methodology primarily focused on traffic management applications. In some cases, the operations strategies presented here may be relatively static (e.g., fixed ramp metering rates or toll rate schedules). However, it is necessary to present these as the starting points in order to analyze the benefits of applying dynamic treatments. It is also recognized that there are several gaps in our knowledge of the effects of ATDM strategies, which can only be filled as more experience is gained with ATDM applications in the United States. It is hoped that the conceptual analysis framework laid out in this Guide will provide the framework for the future research that will fill those gaps.

The analyst can use any traffic operations analysis tool sensitive to ATDM measures (e.g., Highway Capacity Manual, microscopic simulation, mesoscopic simulation) to evaluate ATDM with the methodology described here. For the purposes of this Guide, which is based on HCM-based procedures, the methodology is demonstrated for the facility level only, since the HCM does not currently include system-level analysis. Specifically, the procedure given in Chapter 10 of the HCM (“Freeway Facilities”) is used as the underlying analytical procedure. Layered on top of the Chapter 10 procedure is a “scenario generator” that develops combinations of traffic, disruption, and weather conditions to be analyzed. This requires that multiple runs be made and their outputs combined to develop a complete picture of how a facility operates over time. The scenario generator is a simpler version of the procedure recently developed in Strategic Highway Research Program 2 (SHRP 2) Project L08 (“Incorporating Travel Time Reliability into the HCM”). The SHRP 2-L08 procedure also uses HCM Chapter 10 procedures as the underlying analytical engine but develops a more complete enumeration of the possible conditions affecting a facility’s performance in terms of the variability in traffic demand, incident conditions, weather conditions, and work zones. The limitations of the ATDM Analysis are determined by the limitations of the traffic operations analysis tool used to conduct the Analysis. Where Highway Capacity Manual methods are used for the traffic operations analysis, the analysis is subject to the same limitations as the selected HCM method.

Like all traffic operations analyses, the estimation of delay and other performance measures when evaluating ATDM strategies hinges on the ability of the analyst to identify a large enough study area and study time period to fully cover the geographic and temporal extent of congestion affected by ATDM. Resource limitations will often limit the ability to identify a sufficiently large study area and a sufficiently long study time period for analysis. The analyst must then develop manual corrections to the forecasted performance.

The quality of the analysis depends on the quality of historical data available for estimating how demands and capacities will vary on the facility before and after implementation of ATDM. Six months of historical data on demands, and a year’s worth of historical data on incidents and weather are desirable for evaluating ATDM using the methodology described here. However, reasonable estimates of ATDM performance can be approximated from a 10-day sample of facility demand, as long as the sample adequately represents 6 to 12 months of actual conditions; this can be done by expanding the sample using factors developed on similar facilities or by using default values.

For many ATDM strategies there is relatively little available U.S. experience for assessing the impacts of the strategies on demand, capacity, and speeds. Where data on the effects is lacking for a specific strategy, this Guide provides a “reasonable” estimate of the likely effect that can be used until research or experience provides better information. In such cases, the analyst should use great care in interpreting the results based on these estimated effects and recognize the uncertainty in the results produced using these estimates.

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