Congestion is geographically concentrated in major metropolitan areas, as close to 80 percent of America’s growth and economic development is concentrated in metropolitan areas. Traffic congestion has grown worse in many ways in the past 30 years—trips take longer, congestion affects more of the day and affects more personal trips and freight shipments, and trip travel times are more unreliable. According to AASHTO, travel on the National Highway System has increased fivefold over the past 60 years, from 600 billion miles driven per year to almost 3 trillion in 2009. Annual travel is expected to climb to nearly 4.5 trillion miles by 2050, even with aggressive strategies to cut the rate of growth to only 1 percent per year. The main types of strategies that state and local governments can use to address traffic congestion are improved traffic operations, public transportation, increased capacity, and demand management. ITS generally fits within traffic operations as a way to better manage existing capacity. According to FHWA, traffic congestion is caused by various factors (see fig. 1). Bottlenecks, which reflect inadequate capacity, cause about 40 percent of urban road traffic congestion. The remaining 60 percent of congestion results from other causes, which, according to FHWA, can be addressed by management and operations strategies. ITS encompasses a broad range of wireless and wire line communications-based information and electronic technologies, including technologies for collecting, processing, disseminating, or acting on information in real time to improve the operation and safety of the transportation system. When integrated into the transportation system’s infrastructure and in vehicles themselves, these technologies can relieve congestion, improve safety, and enhance productivity. Using ITS strategies may require officials to make capital improvements by installing equipment, such as traffic control systems and incident management systems. In highly congested metropolitan areas, ITS infrastructure tends to be complex because it typically consists of a set of systems deployed by multiple agencies. For example, the state government typically manages and operates freeway facilities, and city or county governments manage and operate smaller arterial roadways. In a given metropolitan area, the state transportation department, city traffic department, transit agency, and toll authority may each deploy different ITS technologies that address their transportation needs. Metropolitan planning organizations serve a key role in planning, as they have responsibility for the regional transportation planning processes in urbanized areas. Congress established the ITS program in 1991 in the Intermodal Surface Transportation Efficiency Act of 1991 (ISTEA), and DOT created the ITS Joint Program Office in 1994. Since its creation, the ITS Joint Program Office has overseen allocation and expenditure of more than $3 billion for deploying ITS applications and researching new technologies. Under ISTEA and continuing under the Transportation Equity Act for the 21st Century (TEA-21), enacted in 1998, Congress authorized funds specifically for state and local governments to deploy ITS technologies. The Safe, Accountable, Flexible, and Efficient Transportation Equity Act: A Legacy for Users (SAFETEA-LU), enacted in 2005, did not directly reauthorize the ITS deployment program. Although DOT no longer provides dedicated funding for ITS deployment, states can use their federal aid highway program funds for improving traffic operations, including deploying ITS. In addition, state and local governments may use their own funds to finance ITS projects. State funding mainly comes from highway user charges, while local funding primarily comes from general funding allocations, property taxes, sales taxes, and various other taxes and fees. Although DOT does not track state or local spending on ITS, a market research company has estimated that states spent a combined $1.4 billion on ITS in 2010. The ITS Joint Program Office, within RITA, leads research of new ITS technologies and also carries out several activities to promote the use of existing technologies. In this capacity, the office works with the other modal administrations within DOT, including FHWA, the Federal Transit Administration, the Federal Motor Carrier Safety Administration, the Federal Railroad Administration, the National Highway Traffic Safety Administration, and the Maritime Administration. The Joint Program Office was previously housed in FHWA and moved to RITA in early 2006. FHWA’s Office of Operations carries out activities aimed at improving the operations of the surface transportation system, including traffic management, and, as part of these efforts, encourages the use of ITS by state and local governments. State and local governments currently use ITS technologies in a variety of ways to monitor traffic conditions, control traffic flow, and inform travelers. While numerous types of ITS technologies are available for these purposes, their deployment is uneven across the country. We identified several emerging uses of ITS that have significant potential to reduce traffic congestion. These include approaches that use integrated data to manage traffic and inform travelers and use ITS to proactively manage traffic. State and local governments use ITS technologies to monitor traffic conditions, control traffic flow, and inform travelers about traffic conditions so they can decide whether to use alternative, less congested routes (see fig. 2). Transportation agencies use ITS technologies, such as closed circuit cameras and sensors, to monitor traffic conditions in real time. The availability of real-time information means that agency staff can more rapidly identify and respond to events that impede traffic flow, and develop accurate traveler information. For example, cameras are an important component of incident management. Incident management is a planned and coordinated process to detect, respond to, and clear traffic incidents that can cause traffic jams. Operators can use information from cameras to verify traffic conditions detected through sensors, coordinate response to incidents, and monitor the recovery from the incident. According to DOT’s 2010 ITS deployment survey, the percentage of freeway miles covered by cameras increased from approximately 15 The 2010 deployment survey percent in 2000 to 45 percent in 2010.found that 83 percent of freeway management agencies reported a major benefit from cameras—higher than for any other technology. Meanwhile, the level of deployment of cameras on arterials has remained relatively flat. For example, in the 2000 deployment survey, 17 percent of agencies reported deploying cameras on arterials, compared with 21 percent of agencies in 2010. DOT speculated that this may be due to funding limitations at local agencies. Loop detectors use a fixed roadway sensor to measure the number and estimate the speed of passing vehicles. Radar detectors use microwave radar and are mounted on overhead bridges or poles and transmit signals that are reflected off vehicles back to the sensor. The reflected energy is analyzed to produce traffic flow data, such as volume and speed. Vehicle probes use roaming vehicles and portable devices, such as cell phones and Global Positioning System devices, to collect data on travel times. by real-time data collection technologies, as compared with 55 percent in 2010. The use of these technologies has also grown on arterial roadways, with the percentage of signalized intersections covered by electronic data collection technologies growing from approximately 20 percent in 2000 to 48 percent in 2010. In addition, private companies are expanding the use of vehicle probes that collect real-time data on travel time and speed, allowing for greater geographic coverage. Partnering with private companies to gain vehicle probe data expands the data that state DOTs use. According to the 2010 deployment survey, 11 state DOTs reported using vehicle probe data collected by a private sector company. Many technologies can be used to dynamically manage freeway capacity and traffic flow using real-time information. Approximately one-third of the largest U.S. cities deploy traffic control technologies on freeways. Specifically, 35 of the 108 largest metropolitan areas in the United States have deployed one or more of the following freeway technology capabilities: Ramp meters control the flow of vehicles entering the freeway. According to DOT’s 2010 deployment survey, ramp meters are deployed in 27 of the 108 largest metropolitan areas in the country and manage access to 13 percent of freeway miles, about the same level as in 2006. Congestion (or road) pricing controls traffic flow by assessing tolls that vary with the level of congestion and the time of day. All U.S. congestion pricing projects in operation are High Occupancy Toll lanes, which charge solo drivers a toll to use carpool lanes, or peak- period pricing projects, which charge a lower toll on already tolled roads, bridges, and tunnels during off-peak periods. The deployment of congestion pricing relies on electronic tolling ITS technology. Other ITS technologies used to support congestion pricing include sensors that detect traffic conditions and dynamic message signs that announce toll rates. In 2012, GAO found that congestion pricing projects were open to traffic in 14 major metropolitan areas. Reversible flow lanes and variable speed limits can also be used to control freeway traffic and address congestion. These strategies can incorporate various forms of ITS technologies, including retractable access gates and dynamic message signs. According to the 2010 deployment survey, 11 metropolitan areas use reversible flow lanes or variable speed limits on freeways. Transportation agencies can use ITS technologies to control arterial traffic through traffic signals. Types of advanced traffic signal systems include the following: Operating signals under computerized control: This capability allows operators to remotely adjust the signals from the traffic management center to respond to current traffic conditions and allows for enhanced control over signals in response to traffic events. According to the 2010 deployment survey, 50 percent of signalized intersections were under centralized computer control—essentially equal to the proportion in 2000. Adaptive signal control technology: These signals can be automated to adjust signal timings in real time based on current traffic conditions, demand, and system capacity. It allows faster responses to traffic conditions caused by special events or traffic incidents. For example, Los Angeles has developed one of the first fully operating adaptive signal control systems in North America. Despite benefits of adaptive signals, according to DOT, only 3 percent of traffic signals in the country’s largest metropolitan areas are controlled by adaptive signal control. According to DOT, agencies have not deployed adaptive signals because of the costs of deploying, operating, and maintaining them, as well as uncertainty about their benefits.