5.0 Summary, Conclusions, and Next Steps

The objective of the ICM initiative is to demonstrate how ITS technologies can efficiently and proactively manage the movement of people and goods in major transportation corridors. The objectives of the “ICM – Tools, Strategies, and Deployment Support” project are to refine Analysis Modeling and Simulation tools and strategies; assess Pioneer Site data capabilities; conduct AMS for up to four Stage 2 ICM Pioneer Sites; and conduct AMS tools post-demonstration evaluations. Efforts under this project focus on analyzing the ICM systems proposed by the Stage 2 Pioneer AMS Sites, and evaluating the expected benefits to be derived from implementing those ICM systems. The overall benefits of this effort include the following:

Helping decision-makers identify gaps, evaluate ICM strategies, and invest in the best combination of strategies that would minimize congestion and improve safety;
Helping estimate the benefit resulting from ICM across different transportation modes and traffic control systems; and
Transferring knowledge about analysis methodologies, tools, and possible benefits of ICM strategies to the Pioneer Sites and to the entire transportation community.

This document provides a discussion of potential ICM analytical approaches for the assessment of generic corridor operations. The AMS framework described in this report is based on the analysis of advantages and deficiencies of existing tools, and the identification of cost-effective and low-risk strategies to integrate existing tools into an internally-consistent and flexible system approach that is able to support various ICM functional requirements. This document outlines a range of potential analytical approaches for the assessment of corridor operations, and includes a description of the proposed methodological approaches.

At the outset of this effort, existing candidate AMS tools were evaluated and compared for their ability to model ICM strategies and other requirements. Findings from this evaluation reveal that existing models share certain common features, but vary widely in their implementations and data requirements. Most existing tools do not fully integrate the representation of transit services with other auto-based traffic flow and facilities. Also, most of these tools are designed to model recurrent congestion conditions. Modeling non-recurrent congestion conditions requires integration with macroscopic travel demand models and possibly other special modeling techniques. In summary:

Every tool type represents a tradeoff between geographic scope and level of resolution (scale vs. complexity). Less detailed tool types are tractable for large networks, while more detailed tool types are restricted to smaller networks. Depending on corridor size and the types of analyses required, all tool types are potentially valuable for ICM AMS.
Microscopic and mesoscopic simulation models are capable of modeling traveler information strategies, while travel demand models do not have this capability. However, the limited geographic scale of microscopic simulation model implementations makes them less effective choices for traveler information evaluations that involve more than just changeable message signs. The most significant trip choices are made pre-trip or very early in longer trips, and mesoscopic simulation models are more effective than other tool types in evaluating pre-trip and en-route traveler information. Desired capabilities in ICM AMS are more than the capabilities found in existing tools.
“Improve operational efficiency…” refers to system optimization strategies, such as freeway ramp metering and arterial traffic signal coordination. Microscopic simulation models are effective at analyzing these strategies. Mesoscopic simulation models are less effective, and travel demand models do not have this analysis capability.
Travel demand models are better than other existing tools in estimating mode shift, but microscopic and mesoscopic simulation models are better at estimating route shifts. In fact, mesoscopic tools can estimate regional dynamic diversion of traffic, while microscopic tools can estimate route shift at a smaller geographic scale. Also, all travel demand models are capable of analyzing mode-shift, while this capability is very limited in macroscopic simulation models and non-existent in mesoscopic simulation models.
Finally, mesoscopic simulation tools are better at analyzing traveler responses to congestion pricing, but the ICM AMS desired analysis capability is more than what is offered by existing tools.

Three findings emerge from the analysis of capabilities found in existing AMS tools:

Each tool type has different advantages and limitations, and is better than other tool types at some analysis capabilities. There is no one tool type at this point in time that can successfully address the analysis capabilities required by the ICM program. An integrated approach can support corridor management planning, design, and operations by combining the capabilities of existing tools.
Key modeling gaps in existing tool’s capabilities include: a) the analysis of traveler responses to traveler information; b) the analysis of strategies related to tolling/HOT lanes/congestion pricing; and c) the analysis of mode shift and transit.
Interfacing between travel demand models, mesoscopic simulation models, and microscopic simulation models presents integration challenges that can be addressed by identifying interface requirements that focus on: a) maintaining the consistency across analytical approaches in the different tools, and b) maintaining the consistency of performance measures used in the different tool types.

The proposed generic AMS methodology encompasses tools with different traffic analysis resolutions. Three classes of simulation modeling approaches – macroscopic, mesoscopic, and microscopic – are considered essential components of a general AMS methodology. To conduct the analysis of a corridor where ICM approaches and strategies may be implemented, the AMS capabilities need to provide for the interaction of various aspects of macroscopic-, mesoscopic-, and microscopic-level analysis capabilities. The proposed AMS methodology includes:

Macroscopic trip table manipulation for the determination of overall trip patterns;
Mesoscopic analysis of the impact of driver behavior in reaction to ICM strategies (both within and between modes); and,
Microscopic analysis of the impact of traffic control strategies at roadway junctions (such as arterial intersections or freeway interchanges).

The individual modeling approach developed for a specific corridor might involve significant tailoring of the general methodological approach. Depending on the scope, complexity, and questions to be answered within a specific corridor, there may be more or less emphasis on each of the three general model types and their interaction.

In the traffic analysis marketplace, there are suites of tools developed by software vendors that offer some of the proposed analysis capabilities within a single modeling framework. While it might have been simpler to mandate the use of a single unified model/tool, this would: 1) make the transferability of this methodology more difficult; 2) not take into account the models available at the different Pioneer Sites and require more resources for the AMS; and 3) violate the vendor-neutrality principle outlined in Chapter 1.0.

The following key components of the AMS methodology and additional insight into its applicability to different types of corridors include:

Different ICM applications will call for different levels and forms of model integration. For example, assessing the operational efficiency at network junctions and interfaces requires the integration of mesoscopic and microscopic models; whereas, assessing modal shifts calls for the use of all three classes in a coherent manner (i.e., using macroscopic models for demand estimation, mesoscopic models for flow re-distribution, and microscopic models for traffic control optimization).

The proposed ICM AMS methodology will be adapted for and implemented on the Test Corridor. Emphasis has been placed on choosing a methodology that provides the greatest degree of flexibility and robustness in supporting subsequent tasks for the Test Corridor and AMS support of Pioneer Sites.

The proposed methodology includes the development of a simple pivot-point mode shift model and a transit travel time estimation module to support comparison of network and modal alternatives, and facilitate the analysis of traveler shifts among different transportation modes.

The proposed methodology also includes the development of linkage mechanisms required to establish consistency between the modeling resolutions of the AMS candidate tools. Three types of interfaces are generally required to allow communications between macroscopic travel demand models, mesoscopic simulation models, and microscopic simulation models: 1) an interface focusing on network features; 2) an interface focusing on the temporal distribution of trips; and 3) an interface focusing on the refinement/aggregation of model traffic analysis zones that generate and attract travel demand.

5.1 Next Steps

Next steps in the ICM AMS project are summarized as follows:

In Task 2.4, the AMS methodology will be customized and refined for the Test Corridor. This refinement will involve testing of various components on actual or hypothetical corridor settings so as to validate the correctness of the integrated tools. This step will ensure that the integration does not cause undesired effects, and will address and resolve any modeling or data issues before the integrated model is implemented on the Test Corridor.
In Task 2.5, the refined methodology will be applied to the Test Corridor. The purpose of this task is to demonstrate the depth and scope of the analyses that will be conducted as part of the ICM Stage 2 Pioneer AMS Sites. The AMS methodology will be implemented to evaluate a number of ICM strategies; calibrate/‌validate the AMS tool; produce performance measures for each strategy by mode, jurisdiction, and facility type; and tally the results. We will document the results of the Test Corridor AMS activities and findings in a draft and final report. The report will detail the AMS approach, results, lessons learned, and comment on possible limitations of tools with respect to each of the ICM strategies.
In Task 2.6, we will refine the ICM operational strategies based on the results of the Test Corridor AMS in Task 2.5, and propose additional methods to assess ICM strategies. In this task, we will assess the capabilities of AMS methodologies and support cost-benefit calculations for each strategy with the goal of establishing priorities for implementation.
In Task 2.7, we will document the previously developed tools and strategies in a final report. The final report will document lessons-learned from the application of the AMS methodology on the test corridor, and will present the modified AMS methodologies. In addition to documenting the AMS methodologies, the documentation will include a categorization of AMS tools and interfaces to be used in different corridor settings; for different ICM strategies to be modeled; for different types of analysis scenarios; desired performance measures allowing for consistent comparison of ICM strategies; recommended validation/calibration steps and targets; the relative capability of the AMS activity to support benefit-cost assessment for the successful implementation of ICM; potential risks and applicability; and schedule/budget guidelines for ICM AMS activities. This information will be organized in a way that can be useful in determining Decision Point #2 – Site Application Feasibility, and in the development of the Phase 4 – Technology Transfer activities.
In Task 4, we will model the selected Stage 2 Pioneer AMS Sites and analyze their proposed ICM corridor strategies. For each of up to four selected Stage 2 Pioneer AMS Sites, we will: 1) develop site-specific AMS plans; 2) assemble/collect data; 3) assemble available tools, including travel demand models, macro-, meso-, and micro-simulation models, apply any additional tools that may be needed, and build interfaces among these tools using Task 2 methodologies; 4) calibrate/‌validate the baseline models; 5) test ICM strategies using the calibrated models; 6) produce performance measures for each site and scenario; and 7) for each site, prepare a Stage 2 Pioneer AMS Site Assessment Report, detailing the approach, results and lessons learned, and presenting the possible benefits of implementing the proposed ICM strategies.

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