Integrated Corridor Management
Analysis, modeling, and simulations of ICM strategies are going forward on three of the Nation's busiest roadways. Coming next -- demonstrations.
Although high fuel prices and a struggling economy have reduced the number of vehicles on U.S. roadways, traffic congestion remains a costly problem that will only worsen after the economy improves. The Texas Transportation Institute reports that even with the decline in the congestion curve, Americans lost an estimated 4.2 billion hours of time and wasted 2.8 billion gallons of fuel in 2007 as a result of traffic congestion, which translates to an estimated $87 billion hit to the U.S. economy.
The greatest concentrations of congestion occur along critical transportation corridors, which link residential areas, business centers, sports arenas, and shopping areas. Integrated corridor management (ICM) -- the coordination of transportation operations to improve travel management -- is a key strategy to address traffic congestion. ICM research involving analysis, modeling, and simulation at a test corridor (I-880 in San Francisco, CA) and preliminary results from three other analysis, modeling, and simulation pioneer sites (Dallas, TX; Minneapolis, MN; and San Diego, CA) indicate that corridors that implement ICM can expect greater travel time reliability and productivity of corridor networks, and reduced fuel consumption and emissions.
The ICM Initiative, which the U.S. Department of Transportation (USDOT) launched in 2006, now is moving from the basic initial research and preliminary studies at pioneer sites to the demonstration phase. "The initiative's end goal is to demonstrate the value of thinking holistically about how to operate a multimodal transportation corridor," says Dr. Robert Bertini, deputy administrator of the Research and Innovative Technology Administration (RITA). "ICM is a key multimodal tool in the transportation management toolbox, and we are equipping transportation professionals across the country to successfully implement ICM in their corridors through knowledge and technology transfer."
What Is ICM?
ICM enables departments of transportation (DOTs) to optimize use of available infrastructure by directing travelers to underutilized capacity in a transportation corridor. Strategies include motorists shifting their trip departure times, routes, or modal choices, or DOTs dynamically adjusting capacity by changing metering rates at entrance ramps or adjusting traffic signal timings to accommodate demand fluctuations. In an ICM corridor, travelers can shift to transportation alternatives -- even during the course of their trips -- in response to changing traffic conditions.
Multijurisdictional partner agencies manage ICM corridors as collaborative, multimodal systems. At the Federal level, three USDOT agencies -- RITA, Federal Highway Administration (FHWA), and Federal Transit Administration (FTA) -- are partnering with eight of the Nation's busiest corridors in a multiyear initiative to develop, deploy, and evaluate ICM concepts.
The ICM pioneer sites are located in Oakland and San Diego, CA; Dallas, Houston, and San Antonio, TX; Montgomery County, MD; Seattle, WA; and Minneapolis, MN. All eight sites participated in the ICM Initiative's initial phase, which was completed in 2007 and consisted of developing concepts of operations and system requirements.
A concept of operations describes the "who, what, when, where, why, and how" of an ICM system. It also describes the goals of ICM in a transportation corridor from both the users' and the operators' perspectives, and lays the foundation for subsequent institutional, operational, and technical planning, development, and implementation decisions. The system requirements specifications build on the concepts of operations to provide greater detail about what the ICM system will do.
ICM Analysis, Modeling, And Simulation
The USDOT agencies selected three of the pioneer sites (Dallas, Minneapolis, and San Diego) for further analysis, modeling, and simulation tests of ICM strategies under a variety of conditions. Examples are operating the corridors during planned special events, high traffic congestion, and major incidents.
The tests have four goals. The first objective is to ensure the modeling tools will meet the analysis needs and lead to confidence in the model results. The tests also will enable the researchers to determine whether modeling software available in the marketplace today can be used to perform the analysis necessary for ICM. Third, the tests can help DOTs illustrate potential benefits and refine ICM strategies. Finally, the tests will continue fostering collaboration among ICM's public and private sector champions.
Conducting analysis, modeling, and simulation tests enables corridor partners to identify the most promising strategies and informs decisions for design of ICM systems. For the Dallas pioneer site, for example, Robert Saylor, traffic engineering and operations manager for the Dallas suburb of Richardson, sees a clear benefit in analysis, modeling, and simulation because these tests provide insights and measurable results. "When you think about how to react to congestion or an incident, there are multiple alternatives," he says. "One strategy we are looking at, for example, is deploying an additional DART [Dallas Area Rapid Transit] train, which is a significant investment. Through modeling, we are able to determine whether having another train available on-demand will make enough improvement to make the investment worthwhile."
ICM Scenarios Evaluated During Phase I
|Freeway Incident (Major)|
|Freeway Incident (Minor)|
|Arterial Incident (Major)|
|Arterial Incident (Minor)|
Corridor partners develop performance measures for their ICM objectives. The metrics enable the partners to determine how well the ICM system is working and whether it is accomplishing its goals. The performance measures assess ICM performance in four areas:
- Safety: The number and severity of crashes (that is, fatal, injury, and property damage)
- Mobility: How well the corridor moves people and freight
- Reliability: The relative predictability of the public's travel times
- Emissions and fuel consumption: Impacts of ICM strategies on fuel use and emissions
Benefits of the ICM Methodology
The analysis, modeling, and simulation tests facilitate the selection and application of the most effective ICM strategies. The methodology offers corridor managers the ability to predict which combinations of ICM strategies are likely to be most effective in various conditions.
Analysis, modeling, and simulation also help managers invest in ICM strategies with confidence. Modeling the implications of scenarios in advance enables them to fund the most effective combination of strategies.
In addition, the methodology helps corridor managers continually improve implementation of ICM strategies by updating plans, models, and assumptions based on experience. Managers can integrate the methodology with ICM decision support systems to facilitate predictive, real-time, and scenario-based operational decisionmaking. As defined by R.H. Sprague and H.J. Watson in Decision Support for Management, decision support systems are interactive, computer-based systems that help decisionmakers use historical data and models to identify and solve problems.
The three pioneer sites selected for analysis, modeling, and simulation testing embody a cross section of corridor characteristics and assets, and have well-developed concepts of operations and systems requirements. The three sites evaluated nine transportation scenarios.
Alex Estrella, senior transportation planner with the San Diego Association of Governments, is tracking results at the San Diego site. Analysis, modeling, and simulation tests are "helping us measure corridor benefits of planned investments, while also highlighting key corridor strategies for helping us manage congestion. One of the critical measures for our corridor -- both from operational and user perspectives -- is improvement to travel reliability. Our preliminary results indicate that we will be able to achieve significant improvements through combinations of ICM strategies, especially when there is high demand and during nonrecurrent congestion."
Preliminary results from all three analysis, modeling, and simulation pioneer sites show positive trends. For example, preliminary results in San Diego indicate a 12.6 percent improvement in travel time reliability, and in Minneapolis an 11.8 percent improvement in travel time reliability for eastbound trips along I-394. Preliminary results in Dallas also show improvement in travel time reliability and a 10-year net benefit of deploying ICM strategies of $125 million on its ICM corridor.
Given that ICM is new and has put new requirements on current modeling and analysis tools, the ICM Initiative needed to first define an ICM modeling methodology and approach, and then select actual corridors implementing logical ICM strategies that then could be modeled. Finally, the initiative had to build local models and model the selected strategies at each of the corridors. In the future, the process is expected to be faster, although sites still will need time to define their strategies, develop modeling and analysis tools, and collect data.
The following three improvements resulted from the second phase of the ICM research:
Enhancing capabilities necessary to model ICM. The researchers found that the software models used at the pioneer sites did not have the robust capabilities needed to model multimodal assignments and mode shifts in real time, as well as ramp metering, congestion pricing, and dynamically managed lanes. To overcome this hurdle, the USDOT analysis, modeling, and simulation contractor and pioneer site teams worked with universities and vendors of analysis tools to improve the software so it could model these operational strategies. Today, the software developers have either incorporated enhancements to their standard software package or created external modules that provide more functionality for operational and real-time analysis.
Reliable data are key. To develop dependable models, compare ICM strategies, and build a complete picture of the transportation system, reliable data are essential. Gathering information can have its own challenges, such as knowing where to put detectors, having a way to determine when sensors are down, ascertaining what is going on between detectors, and deciding when to accept or reject field data.
The USDOT team conducted a data gap analysis, developed ways to address the gaps, and identified additional data elements needed to evaluate ICM. The team also developed a process for combining different sources to improve the overall quality of the data. To ensure reliability, agencies need to replace defective sensors quickly and be able to change installation and testing standards for their data collection equipment.
Improving model calibration techniques. The analysis, modeling, and simulation methodology is a significant undertaking and, as such, must rely on trusted, well-calibrated models. Through the ICM Initiative, the USDOT team refined the modeling calibration methodologies and criteria. The research raised confidence levels for modeling a "typical day," developed new methods to calibrate the models for an "incident day," and validated transit and park-and-ride numbers so the models can tell the full ICM story.
In December 2009, the three USDOT agencies selected two of the critical transportation corridors for demonstrations, or living laboratories, in the fight against congestion. The two pioneer sites, located in Dallas and San Diego, will build on past findings to provide a firsthand evaluation of real-world impacts. As part of their experience, the demonstration sites will be able to see the impact of technologies to help prevent the dangers of text messaging and other activities behind the wheel that result in distracted driving. In addition, both Dallas and San Diego will be developing decision support systems to help them make real-time decisions about when and how to implement ICM strategies.
Dallas: U.S. 75 Corridor
The U.S. 75 project is a collaborative effort led by Dallas Area Rapid Transit (DART) in collaboration with USDOT; the cities of Dallas, Plano, Richardson, and University Park; the town of Highland Park; North Central Texas Council of Governments; North Texas Tollway Authority; and the Texas Department of Transportation (TxDOT).
U.S. 75 is a north-south radial corridor that serves commuter, commercial, and regional trips, and is the primary connector from downtown Dallas to the cities to the north. Weekday mainline traffic volumes reach 250,000 vehicles, with another 30,000 vehicles on the frontage roads. The corridor has 167 miles (269 kilometers) of arterial roadways.
The U.S. 75 corridor currently has two concurrent flow-managed, high-occupancy vehicle (HOV) lanes, light rail, bus service, and park-and-ride lots. The corridor sees recurring congestion and a significant number of freeway incidents. Light rail on the DART red line is running at 75 percent capacity, and arterial streets are near capacity during peak periods and are affected by two choke points at the U.S. 75/Lyndon B. Johnson Freeway (I-635) interchange and U.S. 75/President George Bush Turnpike interchange.
DART will contribute $3 million to the $8.3 million project, which will use a transportation management model to predict travel conditions 30 minutes into the future. Those predictions will facilitate diversion of traffic from U.S. 75 to other routes during freeway incidents and special events. Through wireless and Web-based alerts, travelers will have access to real-time information about traffic, public transit, and expected travel times. Another goal of the Dallas research is to improve incident management through interagency communication and coordinated response.
Specific practices that the Dallas team intends to employ include the following:
- Provide comparative travel times to the public and operating agencies for the freeway, HOV lanes, frontage roads, arterial streets, and light-rail transit line.
- Use simulations to predict travel conditions for improved incident response.
- Implement interdependent response plans among agencies.
- Divert traffic to strategic arterials with adaptive control that can adjust signal timing in response to real-time traffic demands.
- Shift travelers to the light-rail system during major incidents on the freeway.
San Diego: I-15 Corridor
The I-15 project is a collaboration led by the San Diego Association of Governments (SANDAG), along with USDOT, the California Department of Transportation, Metropolitan Transit System, North County Transit District, and the cities of San Diego, Poway, and Escondido, in addition to private sector support. The goals are to augment technical management, software and systems development, and cutting-edge innovation.
The interstate is a north-south corridor that runs from S.R. 78 in the north to the S.R. 163 interchange in the south. I-15 is a primary artery for the movement of commuters, goods, and services from inland northern San Diego County to downtown San Diego. Weekday traffic volumes range from 170,000 to 290,000 vehicles on the general purpose lanes. The corridor currently has two reversible high-occupancy toll (HOT) lanes. Approximately 20,000 vehicles use the I-15 express lanes during weekdays, and the corridor experiences recurring congestion.
SANDAG and its partnering agencies will contribute $2.2 million for the $10.9 million project. San Diego will use investments in intelligent transportation systems (ITS) to implement a "smart" transportation management system that combines road sensors, transit management strategies, video, and traveler information to reduce congestion. The smart system will deliver information to commuters via the Internet and message signs, and will enable managers to adjust traffic signals and ramp meters to direct travelers to HOV and HOT lanes, bus rapid transit, and other options.
Examples of practices the SANDAG team intends to employ include the following:
- Provide corridor users with the operational condition of all corridor networks and components, such as comparative travel times, parking space availability, incident information, and expected delays.
- Use a decision support system with real-time simulation, predictive algorithms, and analysis modeling.
- Establish, improve, and automate joint agency action plans.
- Identify means of enhancing corridor management across all networks, including shared control of field devices such as lane controls, traveler information messages, and transit priority.
Looking Ahead: Next Steps
The ICM demonstration phase will have three subphases -- kickoff, design and deployment, and operations and maintenance -- all to be completed between 2010 and 2013. San Diego is scheduled to launch in September 2011, and Dallas will go live in January 2012. In parallel to the demonstration phase, USDOT will be conducting an evaluation of the ICM system to determine whether it will do what it is intended to do: improve situational awareness, enhance response and control, better inform travelers, and improve corridor performance.
Implementation guidance, plans, and results will be available online through the "ICM Knowledgebase" to help other corridors interested in conducting analysis, modeling, and simulation. The Web site will contain resources such as factsheets, concepts of operations from the pioneer sites, system requirements documents, and more.
U.S. Transportation Secretary Ray LaHood says, "These communities are leading the way by using state-of-the-art technologies to create a commute that is safer, less congested, and more convenient. America can't simply build our way to a more modern and efficient transportation infrastructure. These projects will show the rest of the Nation that bumper-to-bumper traffic doesn't have to be the status quo."
Brian Cronin is the RITA ITS Joint Program Office (JPO) manager for the ICM Initiative. Cronin is the team leader for ITS research and demonstration for JPO and serves as the technical representative for the Montgomery County and San Antonio pioneer sites.
Steve Mortensen is a senior ITS engineer with the FTA Office of Research, Demonstration and Innovation. Mortensen is the technical representative for the Dallas and Oakland pioneer sites.
Robert (Bob) Sheehan is a transportation specialist with the FHWA Office of Operations. Sheehan is the technical representative for the San Diego pioneer site.
Dale Thompson is a transportation research specialist with the FHWA Office of Operations Research and Development. Thompson is the technical representative for the Houston, Minneapolis, and Seattle pioneer sites.
For more information and to sign up for the two optional Really Simple Syndication (RSS) feeds to be notified when updates are posted to the "What's New" section of the ICM home page and when resources are added to the "ICM Knowledgebase," see www.its.dot.gov/icms/index.htm. To obtain copies of ICM knowledge and technology transfer resources as they become available, please visit the "ICM Knowledgebase" at www.its.dot.gov/icms/knowledgebase.htm. Contact Brian Cronin at 202-366-8841 or email@example.com, Steve Mortensen at 202-493-0459 or firstname.lastname@example.org, Robert Sheehan at 202-366-6817 or email@example.com, or Dale Thompson at 202-493-3420 or firstname.lastname@example.org.