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|Federal Highway Administration > Publications > Public Roads > Vol. 71 · No. 1 > The Congestion Problem|
Publication Number: FHWA-HRT-07-005
The Congestion Problem
by Regina McElroyand Rich Taylor
What are the causes, what are the consequences, and what can be done?
All road users have experienced traffic congestion, some more than others. Most probably have an intuitive sense of what congestion is and what causes it. Americans know it makes a difference in their lives because it makes them wait in their cars, losing the opportunity to do other things.
Congestion also influences where they choose to live and where they work. In 2003, in Washington, DC, congestion robbed the average commuter of 69 hours. This is the equivalent of nearly 2 workweeks every year that could have been spent with family or friends, volunteering in the community, pursuing a hobby, or even simply resting. Commuters in other major cities report similar losses.
The business community understands congestion. Retailers, manufacturers, and shippers have to adjust their operating practices to compensate for time wasted in traffic. Because of congestion, transporting goods and services to their destinations takes longer.
The associated surprise factor makes congestion even more problematic. Individuals must allow more time to arrive at important appointments. When calculating the time to travel to a given location, they must add a "buffer factor." Often, this means that they arrive early and, once again, must wait.
Businesses interested in just-in-time delivery also must allow a buffer factor. In recent years, the high levels of economic prosperity that this country has enjoyed have been built on the efficiencies of just-in-time delivery. Finely tuned production and distribution systems have enabled companies to operate with tight margins and therefore a competitive edge. Boxes of toothpaste no longer sit in storage rooms waiting for the tubes on the store shelves to be sold. Rather, the retailer and manufacturer know when a tube will be sold and more will be needed. The toothpaste is shipped to the retailer so that it will arrive just in time. Some manufacturers have built their marketing plans on just-in-time delivery. Computers are built to order, for example, and shipped only days after an order is placed. When just-in-time delivery schedules are not met, consumer prices increase and services decrease. Dependable freight transportation enables businesses to be responsive to changes in demand, reduce product cycle times, and decrease inventory holdings.
A Time to Act
Dissatisfaction with the effects of traffic congestion is growing. Not only is congestion increasing in major cities, it is spreading to medium-size communities as well. In many cities, congestion is becoming a subject of political debate.
In October 2006, Secretary of Transportation Mary E. Peters summed up the challenge: "Mobility is one of our country's greatest freedoms, but congestion across all of our transportation modes continues to limit predictable, reliable movement of people and goods, and poses a serious threat to continued economic growth. Congestion no longer affects only roads in larger urban areas, but is spreading across America."
The community of transportation professionals has developed methods and technologies to reduce congestion by making the transportation system operate more efficiently. This issue of Public Roads focuses on the traffic congestion problem and the U.S. Department of Transportation's (USDOT) Congestion Initiative.
Recognizing the growing issue, the USDOT leadership chose congestion reduction as a top transportation priority. In May 2006, USDOT announced the National Strategy to Reduce Congestion on America's Transportation Network (otherwise known as the Congestion Initiative). This initiative focuses on meaningful, near-term reductions in congestion.
The Dimensions of Congestion
Congestion usually is defined in terms of excess vehicles on a portion of roadway at a particular time resulting in speeds that are slower — sometimes much slower — than normal or "free flow" speeds. Travelers experience congestion as unintended stopped or stop-and-go traffic. Congestion in the top 85 urban areas (in terms of population) has grown in the past 20 years — in duration, extent, and intensity.
According to Tim Lomax, a research engineer with the Texas Transportation Institute (TTI), "Since we began analyzing congestion data back in 1982, congestion has grown in pretty much every dimension."
The duration of congestion has increased from 4.5 hours to 7.0 hours per day from 1982 to 2003. Specifically, duration is the percentage of the day with speeds below a threshold of 72 kilometers per hour, kph (45 miles per hour, mph) on a freeway, for example, and 48 kph (30 mph) on an arterial. Peak periods typically stretch for 2 or 3 hours in the morning and evening in metropolitan areas above 1 million people. Larger areas can see 3 or 4 hours of peak periods.
The extent of congestion has grown from 33 to 67 percent of highway travel from 1982 to 2003, indicating that congestion affects more of the transportation system. Many cities, such as Los Angeles, CA, or New York City, NY, have a few sections of road where any daylight hour might see stop-and-go traffic. Weekend traffic delays have become a problem in recreational areas, near major shopping centers and sports arenas, and on some constrained roadways.
The intensity of congestion as measured by the average delay penalty (the extra travel time each day due to congestion) has increased from 13 to 37 percent in the past 20 years. In other words, peak-period trips required 37 percent more travel time in 2003 than a free-flow trip at midday, up from 28 percent 10 years earlier. Trips to work and school take longer, but so do shopping trips, doctor visits, and family outings.
Most of the demographic factors that influence travel demand suggest that without decisive policy changes, congestion will continue to worsen. According to U.S. Census Bureau projections, the total U.S. population is expected to grow by nearly 30 percent between 2000 and 2030 (from 281 million to 363 million). This growth will not be evenly distributed geographically. Although population in the Northeast and Midwest is expected to grow by less than 10 percent, the South and West are projected to grow by more than 40 percent. "Sunbelt" cities are heavily highway-oriented, with little or no rail, light rail, or Bus Rapid Transit service to absorb the increased travel demand. Vehicle miles of travel continue to grow at an annual rate of about 1.7 percent.
A Virtual "Congestion Tax" on Large Urban Areas
The Sources of Congestion
What causes the day-to-day frustrations of traffic congestion? With the exception of physical bottlenecks, the sources of congestion occur with annoying irregularity; nothing is ever the same from one day to the next. In addition to causing delay to travelers, the sources of congestion produce another effect: variability in congested conditions. This variability in congestion is known as travel time reliability, or how reliable day-to-day travel conditions are. Reliability is of intense interest for transportation professionals who deal with congestion.
By its very nature, roadway performance is consistent and repetitive and yet highly variable and unpredictable. It is consistent and repetitive in that the peak usage periods occur regularly and can be predicted with a high degree of reliability (the relative size and timing of rush hour is well known in most communities). At the same time, it is highly variable and unpredictable in that, on any given day, unusual circumstances ranging from flat tires to crashes can change the performance of the roadway dramatically, affecting travel speeds and throughput volumes.
The traveling public experiences these large performance swings, and their expectation of unreliable traffic conditions affects both their view of roadway performance and how, when, and where they choose to travel. If a road is known to have highly variable traffic conditions, a traveler using that road to catch an airplane routinely leaves extra time to get to the airport. In other words, according to the Federal Highway Administration's (FHWA) 2005 Traffic Congestion and Reliability: Trends and Advanced Strategies for Congestion Mitigation, the reliability of this traveler's trip is related directly to the variability in the performance of the route taken.
The Costs of Congestion
The cost of congestion for the 85 urban areas in TTI's The 2005 Urban Mobility Report was estimated to be $63 billion based on the 3.7 billion hours of delay and 2.3 billion gallons of wasted fuel calculated in those areas. This congestion cost to the U.S. economy in 2003 was equivalent to 0.6 percent of the gross domestic product (GDP). Moreover, these congestion costs are growing at 8 percent per year, more than double the growth rate of the economy, so that in 20 years congestion costs are expected to rise to 1.6 percent of GDP.
But these published estimates likely account for less than half of the overall costs of transportation congestion. Additional costs include the following:
The Cost of Congestion to the Economy of the Portland Region, a 2005 report prepared for the Portland [Oregon] Business Alliance, the Port of Portland, and the Oregon Department of Transportation, concluded that increasing congestion would "significantly impact the region's ability to maintain and grow business, as well as our quality of life." More specifically, the report stated that "being a trade hub, Portland's competitiveness is largely dependent on efficient transportation, and congestion threatens the region's economic vitality. Businesses are reporting that traffic congestion is already costing them money."
The report calls for significant investment in transportation and congestion education, stating that "failure to invest adequately in transportation improvements will result in a potential loss valued at $844 million annually by 2025 — that's $782 per household — and 6,500 jobs. It equates to 118,000 hours of vehicle travel per day — that's 28 hours of travel time per household in Oregon annually."
The report also cited specific reactions from the business community to the increased congestion in the Portland area. For example, Sysco Food Services, Inc., opened a new regional distribution center in Spokane, WA, to improve service to its market area because serving its market from Portland was taking too long. Another company, OrePac Building Products, "has increased inventories by 7 to 8 percent to mitigate for congestion delays, which represents a lost opportunity for other investment."
Can the Level of Congestion Be Reduced?
A useful way of thinking about the congestion problem might be to consider transportation as a resource that is incrementally distributed to customers. At present, the resource is limited; there is not enough to meet everyone's requirements. Society has several options: Make more of it (add new capacity), use it more productively (operate the system at peak condition and performance), provide alternatives to highway travel (encourage traffic demand management strategies, such as telecommuting) and ensure that consumption levels accurately reflect individual and commercial requirements and preferences (apply direct charges to users).
The transportation industry is evolving to pursue new ways to finance, design, build, and operate highways. But the industry faces significant challenges. First, the physical system is out of sync with current demands, but capacity additions are increasingly difficult to implement. Second, some in the transportation community have yet to bring their business practices and operating procedures into alignment with the postinterstate construction era (with a heavier emphasis on operating the existing infrastructure to peak performance); their business models are geared more toward project delivery. The transportation industry tends to focus more on outputs than outcomes and may have a difficult time assessing the relative merits of operational strategies and implementing practices to improve operations. And, third, customers fail to link their travel decisions to the resulting impacts of adding additional trips to an already strained system or to the additional costs of these impacts.
Making More of It: Strategic Addition of Capacity
At the beginning of the interstate era, Federal funding provided incentives to build new highways. Today, concerns about air pollution, noise, and urban sprawl often stand in the way of capacity additions. Equally significant, adding new capacity can be enormously expensive and physically challenging.
Despite the barriers, new construction that serves critical strategic purposes must go forward or system performance will continue to decline. The demand for new highway capacity is not only increasing but also is dynamic in nature and location. For example, locations that were rural communities in the early 1960s are now major metropolitan areas. Trade routes are not just east-west, but now, because of the success of the North American Free Trade Agreement, are also north-south. Further, enormous increases in international trade have expanded freight access requirements at seaports and major cargo hubs.
Although widespread capacity increases are a thing of the past, many of the barriers may be addressed through increased expenditures. Environmental concerns may be mitigated and physical challenges overcome (for example, through tunneling). However, the resources to fund such improvements simply are not available through traditional sources. For this reason, many professionals in the transportation community are enthusiastic about the opportunities potentially afforded by public-private partnerships (PPPs) and road pricing. Both of these options provide effective ways of financing, managing, and operating roads while reducing the requirement for public sector contributions. Included within this issue of Public Roads are articles on each of these strategies.
Using It More Productively: System Operations and Management
Capacity constraints arise when physical capacity is insufficient and when capacity is temporarily taken away due to traffic incidents, work zones, inclement weather, or special events. As traffic volumes have grown over time and physical capacity has remained relatively constant, the system has become less able to absorb "surprise" — or nonrecurring — events. In the realm of managing the highway system, the margin for error is very small and continues to decline.
"Operating and managing the system to maintain peak performance is imperative," says FHWA Associate Administrator for Operations Jeffrey F. Paniati. "We must operate the system to maximize system performance in the first place and be prepared to take actions to recover as quickly as possible when disruptions occur. Operational strategies can make a major contribution to effective performance of the highway system."
Such strategies include managing temporary disruptions in a way that will return the system to full capacity quickly; ensuring more effective day-to-day operations through coordinated and up-to-date traffic signal timing and operational improvements to relieve bottlenecks; and providing real-time information about the system so that travelers can make immediate decisions about when, where, and how to travel, and transportation agencies can make immediate adjustments to improve system operations.
Despite the availability of management and operations (M&O) options and their proven benefits, it appears that the transportation community largely has yet to embrace them fully. Much remains to be done before M&O strategies are routinely considered as viable and appropriate strategies for improving highway system performance. This situation arises because many agency organizational structures are legacies of the interstate construction era. In other words, many agencies have not yet transitioned to the current reality that calls more for operating the existing system efficiently than it does for expanding the system. For the most part, many of today's transportation agencies continue to emphasize the delivery of capital projects, not services. Consequently, funding priorities reflect projects and not services, and agency operating practices are not supportive of delivering service-based M&O programs.
FHWA coined the term "the 21st century DOT" to refer to departments of transportation (DOTs) that are well positioned to bring about the optimal operation of their highway facilities. Many agencies are on their way toward becoming 21st century DOTs by changing their cultures, the ways they operate, and the ways they make decisions. Currently underway are two efforts that will provide extra impetus in this natural evolution.
First, the transportation community is exploring approaches for bringing M&O into the planning process. Underscoring the move to link planning and operations are provisions in the Safe, Accountable, Flexible, Efficient Transportation Equity Act: A Legacy for Users (SAFETEA-LU) calling for both the congestion management process and the long-range transportation plan to reflect consideration of M&O strategies. FHWA is advancing a comprehensive program that assists DOTs and metropolitan planning organizations in implementing SAFETEA-LU provisions. In a nutshell, the program lays out a path for transportation agencies to move from the traditional project-oriented planning approach to an approach that is based on outcomes.
Second, FHWA has established a robust program providing guidance, technical assistance, and training in performance measurement. Just as outcome-based performance measures provide the means for linking planning and operations, so too can they link transportation agencies directly to their customers. Performance information explains not only an agency's performance in providing transportation services, but also helps guide agencies (and stakeholders) toward investments and strategies with the highest payoffs for reducing congestion. An emphasis on performance outcomes will provide a common platform for transportation agencies to communicate with their customers. FHWA contends that when the customer understands the value of M&O strategies (and the associated investment tradeoffs) the project-oriented business model will change to one that is more service oriented.
Reducing System Demand: Providing Better Transportation Choices
Just as M&O strategies provide "virtual" capacity additions through more effective operation of the highway system, travel demand management (TDM) initiatives indirectly can change the demands on the system. TDM strategies include parking pricing, transit and vanpool benefits, flexible work schedules, compressed workweeks, telecommuting, satellite work centers, dynamic message signs, and decreased transit fares.
TDM increases the use of travel alternatives; spreads the timing of travel to less congested periods; reduces the need for travel; and shifts the routing of vehicles, including trucks and single-occupant vehicles, to less congested facilities. TDM has the potential to provide travelers with choices of location, route, time, and mode.
Some transportation agencies have yet to take full advantage of the informational, technological, and financial mechanisms available to deploy robust TDM programs. However, a number of trends will facilitate innovative TDM practices. For example, the technologies used for transportation systems and services enable operators to gather, share, and deliver information to travelers through more timely and useful ways. Recent changes in the Federal tax code have made financial mechanisms a more compelling feature of TDM, especially for influencing commuting behavior. Finally, as road-pricing strategies are implemented, TDM options will provide viable alternatives for those not willing or able to pay to travel on a priced facility.
Creating an Efficient Transportation Market: Road Pricing
Although the building of new facilities and better M&O of roads that currently are part of the system are effective strategies in relieving congestion, they do not address one of its root causes: that most travelers do not pay the full cost of receiving transportation services. When making travel decisions, travelers consider only their own travel times and vehicle operating costs; they do not consider the effects that their trips will have on others using the same facilities. This is why congestion often returns to newly constructed facilities, and why facilities with state-of-the-art operating practices remain congested.
In many cases, what occurs today on the highways is rationing by delay. In any market — efficient or not — when demand exceeds supply, the market will find a way to allocate goods and services. In the case of highway travel, a notably inefficient market, travel is distributed according to the amount of time users are willing to wait.
Congestion pricing — charging a price that will bring supply and demand into balance — relies on market forces and recognizes that trip values vary by individual, depending on time, location, destination, and cost, and more broadly among individuals, depending on personal preference and access to alternative travel options.
Congestion pricing incorporates both the direct cost to the traveler and the cost of delay that the traveler imposes on others. Travelers are encouraged to eliminate some lower value trips or take them at different times, or to choose alternate routes or modes of transportation, such as transit or carpooling.
In the United States, priced facilities are in limited use. Where they are operational, priced facilities are highly popular with the public, as evidenced by the acceptance of pricing on I-394 in Minneapolis, MN, and I-15 in San Diego, CA. In other areas, the public is skeptical. FHWA has undertaken an aggressive program to encourage jurisdictions that have extra capacity on their high-occupancy vehicle facilities to consider allowing single-occupant vehicles the choice of using these facilities for a price that varies with demand. This program, combined with the broad congestion pricing demonstrations that will be conducted by the USDOT Urban Partnership program, will address local congestion immediately and will establish the benefits of congestion pricing.
Changing the Paradigm: The Congestion Initiative
USDOT and the transportation community have identified several options to bring about a less congested system that would best serve society: Make more of it, use it more productively, reduce highway system demand, and create an efficient transportation market. The USDOT Congestion Initiative establishes a firm base from which transportation agencies can pursue these options aggressively. In particular, the Urban Partnership program will demonstrate the benefits of congestion pricing (bringing efficiency to the market for highway transportation services). Urban Partnerships also will demonstrate the value of a comprehensive approach that includes transit, TDM, and enhanced system operations.
The Congestion Initiative provides several ways to supplement traditional funding sources and support the introduction of new capacity and maintenance of existing capacity: congestion pricing, PPPs, and facilitation of strategic investment through the Corridors of the Future program.
The Congestion Initiative also focuses on the role that operations and advanced technologies can contribute to congestion reduction. This focus will help transform transportation agencies into 21st century DOTs with a commitment to excellence in service, ready and able to take full advantage of the technologies and applications now available.
In addition to providing key foundational pieces to underpin congestion reduction policies, the Congestion Initiative highlights the serious challenges affecting freight transportation in this country.
All in all, the Congestion Initiative expands the choices available to travelers to include the availability of facilities with guaranteed congestion-free travel, and expands the options available to owners and operators interested in reducing congestion on their facilities.
Congestion affects the day-to-day lives of American citizens as well as commercial enterprises: It degrades productivity, increases consumer costs, influences location decisions, and deprives all Americans of leisure time. The problem is growing, and will not abate unless fundamental reform is made in the way the Nation manages and operates its transportation system. The evidence shows that the status quo in transportation is not working. To provide congestion relief now and in the future, new approaches are needed. The Congestion Initiative is intended to put the Nation on the path to benefiting from those new approaches.
Regina McElroy serves as director of FHWA's Office of Transportation Management. In this position, she manages a staff responsible for FHWA policies and programs related to transportation management and deployment of intelligent transportation systems. She plays a key role in advancing the Congestion Initiative. Formerly, as director of the Office of Transportation Operations, McElroy provided leadership in the areas of traffic incident management, work zones, and road weather management. From 1999 to 2003, she served as team leader in the Office of Asset Management, where she implemented key initiatives to institutionalize the emerging discipline of transportation asset management. She began her transportation career as an economist with the American Trucking Association. She joined FHWA as a transportation specialist in 1987.
Rich Taylor is a transportation specialist with FHWA's Office of Operations. He manages the Operations Performance Measurement program and coordinates congestion mitigation activities for FHWA. He previously served as director of information programs for the Intelligent Transportation Society of America, as an ITS designer with Wilbur Smith Associates, and as a research scientist with the Virginia Department of Transportation. Taylor holds bachelor's and master's degrees in urban planning and a master's degree in civil engineering from the University of Virginia.
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