Traffic Congestion in U.S. Metropolitan Areas: Causes and Solutions

Introduction and Problem Scope

There is an increasing body of evidence that suggests traffic congestion is a growing problem in many metropolitan areas of the United States. Rising traffic congestion can have a significant impact not only on safety considerations, but on federal, regional, state, and local economies, with increases in travel times, air pollution, and fuel usage. Equally, congestion poses important challenges to freight deliveries, supply chains, international trade, and U.S. access to intermodal transportation terminals and infrastructure.

Congestion is an occurrence that is tied to specific geographical locations, where dynamics affect many disciplines on multiple levels. For example, delays at a road intersection can block traffic for extended periods, or a blockage at a port with multiple ships can delay cargo loading and unloading. As a result, individual operators, transportation directors, and planners must recognize and assess the different types of congestion and their impacts on various infrastructures throughout the United States.

Today, the transportation system within the United States is being pushed to its limits. Demands on this multi-modal system will only increase as trends in population growth, technology upgrades, improvements in information technology, and the globalization of economies will significantly impact how the United States competes for success in the global environment (Njord and Meyer, 2005). This research examines one of the most critical issues facing the U.S. transportation system: congestion and its impacts on the nation's economy and citizens' quality of life. Additionally, this study identifies the seven main sources of travel congestion, examines the relevant costs of traffic congestion, and offers dynamic strategies for congestion relief on the U.S. transportation system.

Seven Sources of Traffic Congestion

According to Njord and Meyer, the annual Texas Transportation Institute reports that "congestion has grown everywhere in areas of all sizes as airports, ports, and railroads are straining to meet demand, but highway congestion is most important, because 87 percent of all passenger trips are made in private vehicles" (Njord and Meyer, 2005). This finding underscores why this research study identifies with many of the issues surrounding highway travel due to its symbiotic relationship with the subject of congestion.

Rodrigue et al. write that congestion occurs across multiple means and physical areas and stems from two root principles: "when demand for mobility exceeds the capacity to support it, and when random events bring about a temporary disruption to service, such as an accident or a natural hazard such as flooding" (Rodrigue et al., 2013). The U.S. Department of Transportation's Federal Highway Administration Office of Operations highlights that there are seven main sources, or causes, of congestion, which are then split into three distinct categories.

The first category, identified as "Traffic-Influencing," incorporates three causes of congestion: traffic incidents, work zones, and weather. The second category, labeled "Traffic Demand," includes two causes described as fluctuations in normal traffic and special events. The third category, described as "Physical Highway Features," encompasses two causes determined to be traffic control devices and physical bottlenecks related to the maximum number of vehicles capable of traversing U.S. highways. The problem is easily identified: the demand for highway travel by U.S. citizens continues to grow as population increases, particularly in metropolitan areas, yet the construction of new highway networks has failed to keep pace with this growth.

Between 1980 and 1999, route miles of highways increased by 1.5 percent while vehicle miles of travel increased 76 percent. However, the Federal Highway Administration has recently identified that highway travel within the U.S. has been steadily increasing two to three percent per year over the last decade, with a maximum capacity for most U.S. freeway lanes topping out at 2,050 to 2,200 vehicles per hour. The future holds more of the same expected traffic growth with the same seven sources of congestion. By 2025, the U.S. population will grow by 26 percent, Gross National Product will double in output, and high-capacity truck haul tonnage will grow by 75 percent, meaning heavier forecasts of population and economic activity will correlate into higher levels of congestion throughout metropolitan, urban, and rural areas of the United States.

Within recent years, particularly since the beginning of the 1990s, rising transportation demand and road traffic have led to congestion, delays, accidents, and a host of environmental issues, which have consequences in both economic efficiency and social quality of life. Traffic congestion, commonly referred to as gridlock, can have a critical impact on a citizen's personal life, career, future, and safety, including effects from noise and air pollution. As a result of the two to three percent yearly growth in traffic congestion, the Texas Transportation Institute estimates that in 2011 alone, congestion in 498 metropolitan areas of the United States caused citizens to travel 5.5 billion more hours and to utilize an extra 2.9 billion gallons of fuel.

Economic and Safety Impacts of Congestion

These figures are expected to climb as the Texas Transportation Institute expects the volume of freight capacity (trucking) to nearly double by 2020, making congestion no longer just a big city problem. Within the U.S., freight-line carriers moved approximately 19 billion short tons, worth more than $13 trillion U.S. dollars in 2002 alone, and are expected to increase to 37 billion short tons, worth about $38 trillion U.S. dollars by 2035 (Jones, 2007). The Federal Highway Administration's 2006 Freight Analysis Framework reported that commercial line-haul trucks moved about two-thirds of the value of goods, approximately 60 percent of the freight tonnage in 2002, and this total is expected to grow as the trucking industry carries the bulk of all hauling within the U.S.

With the increase in trucking assets and personally owned vehicles on road networks causing traffic congestion, there is a corollary relationship with an increase in accidents associated with this type of congestion. A 2011 AAA Crashes vs. Congestion study revealed that within 99 key urban areas researched for total vehicle crashes per given timeframe, there were 16,032 fatalities and 1,613,236 injuries with associated financial costs at $299.5 billion. The value of each statistical life was estimated at $6,000,000 and the cost of an injury was evaluated at $126,000. The key finding is that the larger the city, the larger the total cost of crashes, normally where congestion is critically apparent.

Overall, the Cambridge Systematics Inc. report identified that 5.5 million police officials report vehicle crashes totaling 30,000 fatalities and two million injuries throughout the United States on a yearly basis. The numbers of fatalities and injuries are alarming, and U.S. elected officials and the general public are increasingly concerned about the consequences of congestion in the near and far term on the nation's road networks. All of this adds up to a staggering amount of costs and consequences imposed on travelers by traffic congestion, leading many to wonder if anything can be done to slow down future increases in traffic gridlock.