Traffic Congestion and Reliability:
Trends and Advanced Strategies for Congestion Mitigation

Travel Reliability Is Also Getting Worse

Changes in reliability could be considered a fourth characteristic of congestion trends. The extra travel time and amount of the day and system affected by travel delays is not the same every day. It may not even be as it was predicted 10 minutes ago.

• 1982 – If your midday trip took 20 minutes, it would take you 23 minutes in the peak. Although no reliability statistics exist from that long ago, analysis of recent data suggest that you would have to add an additional nine minutes to that trip to guarantee on-time arrival at your destination; a total of 32 minutes might be planned for that trip.
• 2003 – By 2003, that 20-minute free-flow trip took 28 minutes. And if on-time arrival was important you should allow 40 minutes for the trip.

Only in the last few years have the data been available to assess travel time reliability. Atlanta, Georgia is a city with both a history of detailed traffic monitoring data and significant congestion. Table ES.1 shows that travel times grew increasingly unreliable in several highly traveled freeway corridors over a four-year period. This is indicated by increases in the Buffer Index; as it rises, travel times become more unreliable.

 

STRATEGIES TO REDUCE CONGESTION AND IMPROVE RELIABILITY — FOCUS ON OPERATIONS

Transportation engineers and planners have developed a variety of strategies to deal with congestion. These fall into three general categories:

1. Adding More Base Capacity – Increasing the number and size of highways and providing more transit and freight rail service. This can include expanding the base capacity (by adding additional lanes or building new highways) as well as redesigning specific bottlenecks such as interchanges and intersections to increase their capacity.
2. Operating Existing Capacity More Efficiently – Getting more out of what we have.
3. Encouraging Travel and Land Use Patterns that Use the System in Less Congestion Producing Ways – Travel Demand Management (TDM), non-automotive travel modes, and land use management.

All of these strategies can lead to a reduction in congestion, but it is operations strategies that have the most dramatic effect on reliability because they target the sources of unreliable travel directly. Operations strategies focus on the traffic-influencing events that both raise the general level of congestion and increase unreliable travel.

A vast array of strategies are in the transportation professional's "operations toolbox," most of which use advanced technology to identify problems, manage traffic flow, and relay travel conditions to users. Known as Intelligent Transportation Systems (ITS), these technologies enable transportation professionals to implement operations strategies targeted specifically at the causes of unreliable travel:

• Incident Management – Identifying incidents more quickly, improving response times, and managing incident scenes more effectively;
• Work Zone Management – Reducing the amount of time work zones need to be used and moving traffic more effectively through work zones, particularly at peak times;
• Road Weather Management – Prediction of weather events (such as rain, snow, ice, and fog) in specific areas and on specific roadways, allowing for more effective road surface treatment;
• Planned Special Events Traffic Management – Pre-event planning and coordination and traffic control plans;
• Freeway, Arterial, and Corridor Management – Advanced computerized control of traffic signals, ramp meters, and lane usage (lanes that can be reversible, truck-restricted, or exclusively for high occupancy vehicles);
• Traveler Information – Providing travelers with real-time information on roadway conditions, where congestion has formed, how bad it is, and advice on alternative routes; and
• Value Pricing Strategies – Proactively managing demand and available highway capacity by dynamically adjusting the toll paid by users.

FHWA has strongly promoted operations for improving congestion for several years in the form of grants, education and outreach, technical tools, and standards development. State and local transportation agencies, who are responsible for implementing transportation improvement projects, have embraced operations as a key part of their solutions. Operations strategies in the above categories have been effectively deployed around the country to decrease congestion and improve reliability. Many deployments include combinations of strategies, or congestion relief packages, which have proven to be more effective than simply deploying individual strategies. Several of the more significant recent deployments include:

• Arterial Management. Road Commission of Oakland County (RCOC) FAST-TRAC Project – Advanced Traffic Signal Coordination. Oakland County, located just north of Detroit, began implementation of the FAST-TRAC (Faster and Safer Travel through Traffic Routing and Advanced Controls) system in 1992. The key element of FAST-TRAC is the Sydney Coordinated Adaptive Traffic System (SCATS), an advanced adaptive signal system with the capability to adjust signals on an individual intersection, corridor, and areawide basis. The system detects real-time demand on the highways and continuously adjusts signal timing to meet the demand. The result is that FAST-TRAC reduces congestion by eliminating unnecessary stops and providing green phases where the demand is highest.
• Freeway Management and Incident Management. Wisconsin District 2 Freeway System Operational Assessment (FSOA) Program – Integrated Congestion Relief Strategies. During the 1990s Wisconsin DOT's District 2 implemented a freeway management system in Milwaukee. The freeway management center, field equipment, and central computer system are known as the MONITOR system. Expansion continued into the early 2000s until most of the Milwaukee area's major freeways were covered with detectors along 130 miles of freeway, 18 cameras located at major interchanges, 20 Dynamic Message Signs to communicate with motorists, over 80 ramp meters, freeway service patrols, and trailblazer systems to aid in rerouting traffic during traffic incidents, construction, and other emergencies. The program is coordinated with several other related efforts including WisDOT's statewide SmartWays Program and the Gary-Chicago-Milwaukee Corridor Coalition (GCM). The ramp meters keep the freeway operating at steady flow for longer periods of time than otherwise could be expected. The service patrols and cameras allow for quicker identification of and response to incidents, a major source of unreliable travel.
• Incident Management. Maryland's Coordinated Highway Action Response Team (CHART) – Statewide Traffic Incident Management. Maryland developed the Coordinated Highway Action Response Team (CHART) in the mid 1980s as an effort to improve travel to and from the state's coastal area. Years later, this system has evolved into a statewide operations tool that collects, processes and broadcasts traffic information. Data are collected through a communications infrastructure, a closed-circuit television system, and sensor detection system. The information is then used to make real-time traffic management decisions and provide motorists with information through dynamic message signs, radio travel advisories, and a telephone advisory system. Travelers may also access an interactive on-line GIS mapping service for major roads to obtain average speed, traffic conditions, and lane closures due to weather or construction activities. In addition, travelers can view selected road conditions through on-line video links. By reducing the duration of incidents and providing travelers with advanced warning of their locations, travel reliability is improved.
• Corridor Management, Incident Management, and Traveler Information. Seattle's Integrated Operations Programs. The Washington State DOT has been aggressively pursuing operations-oriented improvements for many years. An innovative combination of technology, policies, and resource allocation has provided travelers in Washington with more reliable travel times, reduced collisions and more efficient use of the available funding. Key aspects of the approach include: incident management; ramp metering; short, selected capacity increases; travel conditions and commute time information; high-occupancy vehicle lanes and public transportation facilities; and readily understood performance measures. As with the Wisconsin and Maryland projects, aggressive incident management practices in Seattle reduce the delay caused by incidents and improve travel reliability.
• Work Zone Management, Corridor Management, and Value Pricing. Houston's Accelerated Construction of the Katy Freeway – The Systems Approach to Bottleneck Removal. The Katy Freeway (I-10 West in Houston) expansion project is being constructed using an innovative combination of construction and financing techniques. The project, in broad terms, results in a six-year construction program, (compared to the 12-year original schedule), provides a four-lane tollway in the middle of an expanded freeway, improves the aesthetic and landscaping treatments in the corridor, and rebuilds the existing freeway pavement and bridges.

Houston's Katy Freeway improvement project highlights an emerging and highly promising operations strategy: value pricing of managed lanes. In this approach, certain travel lanes are set aside for high occupancy vehicles, toll priced for other vehicles, or both. On the Katy Freeway, travelers in buses and carpools, currently restricted to a three-person requirement in the peak hours (2-person requirement during other hours) due to limited capacity in the HOV lane, will be able to travel in the free-flow managed lanes. All travelers will have shorter time periods of congested conditions in the peak, and should have much less stop-and-go traffic in the off-peak. The managed lanes will also provide choices—free, but congested lanes, bus or carpool use of the managed lanes for free or reduced price, and a premium pay-for-travel system that allows travelers to determine the importance of their trip and pay for faster, more reliable travel if they so choose.

PROMISING OPERATIONS STRATEGIES ON THE HORIZON

In addition to innovative projects that have already been implemented, a number of even more advanced technologies and integrated programs are in development. These programs and technologies offer great promise for addressing congestion problems in the near future. A review of several such programs and technologies follows.

iFlorida: Testbed for the Next Generation of Operations Strategies. (Freeway, Arterial, and Corridor Management; Road Weather Management; and Traveler Information). In March 2003, the Florida Department of Transportation (FDOT) was selected to participate in a highly innovative model deployment of operational strategies with FHWA. Named iFlorida, this project is based on the idea that advanced operational strategies require highly detailed traffic condition data over a wide area. Therefore, the initial stages of the project are to deploy additional traffic surveillance equipment to augment FDOT's existing information infrastructure. Once in place, the infrastructure will be used to demonstrate the wide variety of advanced operational functions to enhance traffic flow and improve security, including:

• Advanced weather information;
• Security monitoring command and control;
• Variable speed limit trial;
• Roadway diversion information;
• Statewide and central Florida traveler information web sites;
• On-board video surveillance on Orlando City buses; and
• Evacuation operations.

Integrated Corridor Management ITS Initiative. (Freeway, Arterial, and Corridor Management). Recognizing the importance of maximizing the operational effectiveness of an entire corridor, the U.S. DOT's ITS program includes "Integrated Corridor Management" (ICM) Systems as one of nine Major Initiatives. The basic premise behind the ICM initiative is that these independent systems and their cross—network linkages could be operated in a more coordinated and integrated manner resulting in significant improved operations across the corridor. As stated in the ICM vision, "metropolitan areas will realize significant improvements in the efficient movement of people and goods through aggressive and proactive integration and management of major transportation corridors." In essence, integrated corridor management consists of the operational coordination of specific transportation networks and cross-network connections comprising a corridor, and the coordination of institutions responsible for corridor mobility. The goal of the Integrated Corridor Management Initiative is to provide the institutional guidance, operational capabilities, and ITS technology and technical methods needed for effective Integrated Corridor Management Systems. Currently, the ICM initiative consists of the following four phases:

1. Foundational Research;
2. Operations and Systems Development;
3. Model Deployment; and
4. Knowledge and Technology Transfer.

Clarus Weather Initiative: Weather Prediction and Monitoring at the Roadway Level. (Road Weather Management). Clarus (which is Latin for "clear") is an initiative to develop and demonstrate an integrated surface transportation weather observation data management system, and to establish a partnership to create a nationwide surface transportation weather observing and forecasting system. The objective of Clarus is to enable weather service providers to provide enhanced information to all road, rail and transit managers, and users to reduce the effects of adverse weather (e.g., fatalities, injuries, and delay). The Clarus Initiative aims to demonstrate how an open, integrated approach to observational data management can be used to consolidate surface transportation environmental data. Surface transportation environmental data assimilated by the Clarus system will include atmospheric data, pavement and subsurface data, as well as hydrologic (water level) data.

NEXT STEPS: BUILDING THE FOUNDATION FOR EFFECTIVE TRANSPORTATION OPERATIONS

Transportation operations can reduce the growth of congestion and improve the reliability of travel conditions for highway users. By directly targeting the sources of unreliable travel through transportation operations, the chances of unexpected and extreme congestion are greatly reduced, enabling travelers to experience more consistent conditions from day-to-day. Maximizing the potential of transportation operations requires much more than just deploying advanced technology. Meeting customer expectations for safe, reliable, and secure transportation services also requires that planners and system operators coordinate better so that operations can be strategically planned and deployed; so that operations data and system information is routinely shared among system operators, service providers, and transportation planners; and so that performance is continuously monitored to provide the feedback necessary to adapt to changing conditions and properly plan for future demands. These three important aspects of transportation operations are addressed below.

COORDINATION BETWEEN PLANNING AND OPERATIONS

The operation of the transportation system and planning for the transportation system are often two detached sets of activities with different requirements and different cultures. Management and operation of the transportation system typically involves a different set of practitioners with a short-term or real-time focus, often with little consideration of how activities relate to a regional transportation systems long-term goals and objectives. Transportation planning has traditionally relied upon long-range travel needs, goals for a region, and funding constraints with little consideration of short-term and ongoing operational issues. Transportation agencies, metropolitan planning organizations (MPOs), and other stakeholders are increasingly recognizing the value of coordination and collaboration among planners and operators. Although they come from differing perspectives, transportation planning and operating agencies generally share the goal of enhancing system performance, and they can benefit from stronger linkages. The major point is that while each group has its own priorities, both planners and operators need to be involved in all phases of the project development timeline.

SHARING DATA EFFECTIVELY: USING OPERATIONS DATA FOR IMPROVED OPERATIONS

Most major metropolitan areas have advanced technologies deployed to monitor traffic conditions. The data are used in real-time to identify traffic back-ups, re-time traffic signals and ramp meters, and for estimating travel times along highway segments. The data is extremely valuable when stored and used to develop historic trends. In fact, the highly detailed nature of the data (typically collected every 20 to 30 seconds at one-half-mile intervals on freeways) allows transportation operators to conduct many types of analyses previously unavailable to the profession. Foremost among these is the estimation of reliability, which requires continuously collected data in order to build a sufficient history of how travel conditions vary over time.³ The data also provides the basis for adjusting operations control strategies such as re-timing signals, deploying additional equipment, and implementing diversion and evacuation plans.

Data sharing may take several forms. For example, operations data could be archived for analysis and used in a number of transportation planning applications, such as calibration of systems planning models, use in micro-simulation models, or for performance monitoring of the transportation system. Effective data sharing can occur in several ways:

• Develop a regional data clearinghouse;
• Coordinate data resources with transit agencies;
• Use special events to initiate new data partnerships;
• Use operations data to develop more effective performance measures and improve planning analysis tools; and
• Use archived data to inform management and operations planning.

MARKING PROGRESS THROUGH PERFORMANCE MEASUREMENT

In the last few years, transportation operators have increasingly embraced the concept of performance measurement—tracking the trends of key indicators of how the transportation system is performing. Performance measurement has been widely used in the private sector as a way to improve delivery of goods and services to customers and ultimately, the success of the enterprise. Fundamentally, this is no different from providing improved transportation services to the public—public agencies are businesses "selling" transportation service and travelers are the consumers "buying" them.

Perhaps the most significant lesson from the review of performance measurement activities over the last two decades is that all performance measures and measurement systems have evolved. The changes have been the result of legislative interests, accountability efforts, new data sources, estimation procedures, changes in knowledge about traffic conditions, and, perhaps most importantly, growth in demand for the information once reports and data are used. Transportation staff and leaders should experiment with measures, data, and presentation techniques.