DOT is working with the automobile industry, state and local transportation agencies, researchers, private sector stakeholders, and others to lead and fund research on connected vehicle technologies to enable safe wireless communications among vehicles, infrastructure, and travelers’ personal communications devices. Connected vehicle technologies include vehicle-to-vehicle (V2V) and vehicle-to-infrastructure (V2I) technologies: V2V technologies transmit data between vehicles to enable applications that can warn drivers about potential collisions. Specifically, V2V-equipped cars would emit data on their speed, position, heading, acceleration, size, brake status, and other data (referred to as the “basic safety message”) 10 times per second to the on-board equipment of surrounding vehicles, which would interpret the data and provide warnings to the driver as needed. For example, drivers may receive a forward collision warning when their vehicle is close to colliding with the vehicle in front of them. V2V technologies have a greater range of detection than existing sensor-based crash avoidance technologies available in some new vehicles. NHTSA is pursuing actions to require that vehicle manufacturers install the underlying V2V technologies that would enable V2V applications in new passenger cars and light truck vehicles, and requested comment on this issue in an August 2014 Advanced Notice of Proposed Rulemaking. We reported on V2V technologies in November 2013. Thus, we are not focusing on these technologies in this report. Vehicle-to-infrastructure (V2I) technologies transmit data between vehicles and the road infrastructure to enable a variety of safety, mobility, and environmental applications. V2I applications are designed to avoid or mitigate vehicle crashes, particularly those crash scenarios not addressed by V2V alone, as well as provide mobility and environmental benefits. Unlike V2V, DOT is not considering mandating the deployment of V2I technologies. V2I applications rely on data sent between vehicles and infrastructure to provide alerts and advice to drivers. For example, the Spot Weather Impact Warning application is designed to detect unsafe weather conditions, such as ice or fog, and notify the driver if reduced speed or an alternative route is recommended (see left side of figure 1). DOT is also investigating the development of V2I mobility and environmental applications. For example, the Eco-Approach and Departure at Signalized Intersections application alerts drivers of the most eco-friendly speed for approaching and departing signalized intersections to minimize stop-and- go traffic and idling (see right side of fig. 1), and eco-lanes, combined with eco-speed harmonization, (demonstrated in the following video) would provide speed limit advice to minimize congestion and maintain consistent speeds among vehicles in dedicated lanes. DOT is also pursuing the development of V2I mobility applications that are designed to provide traffic signal priority to certain types of vehicles, such as emergency responders or transit vehicles. In addition, other types of V2I mobility applications could capture data from vehicles and infrastructure (for example, data on current traffic volumes and speed) and relay real-time traffic data to transportation system managers and drivers. For example, after receiving data indicating vehicles on a particular roadway were not moving, transportation system managers could adjust traffic signals in response to the conditions, or alert drivers of alternative routes via dynamic message signs located along the roadway. In addition to receiving alerts via message signs, these applications could also allow drivers to receive warnings through on-board systems or personal devices. Japan has pursued this approach through its ITS Spot V2I initiative, which uses roadside devices located along expressways to simultaneously collect data from vehicles to allow traffic managers to identify congestion, while also providing information to drivers regarding upcoming congestion and alternative routes. To communicate in a connected vehicle environment, vehicles and infrastructure must be equipped with dedicated short-range communications (DSRC), a wireless technology that enables vehicles and infrastructure to transmit and receive messages over a range of about 300 meters (nearly 1,000 feet). As previously noted, V2V- equipped cars emit data on their speed, position, heading, acceleration, size, brake status, and other data (referred to as the “basic safety message”) 10 times per second to the surrounding vehicles and infrastructure. V2I-equipped infrastructure can also transmit data to vehicles, which can be used by on-board applications to issue appropriate warnings to the driver when needed. According to DOT, DSRC is considered critical for safety applications due to its low latency, high reliability, and consistent availability. In addition, DSRC also transmits in a broadcast mode, providing data to all potential users at the same time. Stakeholders and federal agencies have noted that DSRC’s ability to reliably transfer messages between infrastructure and rapidly moving vehicles is an essential component to detecting and preventing potential collisions. DSRC technology uses radiofrequency spectrum to wirelessly send and receive data. The Federal Communications Commission (FCC), which manages spectrum for nonfederal users, including commercial, private, and state and local government users, allocated 75 megahertz (MHz) of spectrum—the 5.850 to 5.925 gigahertz (GHz) band (5.9 GHz band)—for the primary purpose of improving transportation safety and adopted basic technical rules for DSRC operations. However, in response to increased demands for spectrum, FCC has requested comment on allowing other devices to “share” the 5.9 GHz band with DSRC technologies. V2I equipment may vary depending on the location and the type of application being used, although in general, V2I components in the connected vehicle environment include an array of roadside equipment (RSE) that transmits and receives messages with vehicles for the purpose of supporting V2I applications (see figure 2). For example, a V2I- equipped intersection would include: Roadside units (RSU)—a device that operates from a fixed position and transmits data to vehicles. This typically refers to a DSRC radio, which is used for safety-critical applications that cannot tolerate interruption, although DOT has noted that other technologies may be used for non-safety-critical applications. A traffic signal controller that generates the Signal Phase and Timing (SPaT) message, which includes the signal phase (green, yellow, and red) and the minimum and maximum allowable time remaining for the phase for each approach lane to an intersection. The controller transfers that information to the RSU, which broadcasts the message to vehicles. A local or state back office, private operator, or traffic management center that collects and processes aggregated data from the roads and vehicles. As previously noted, these traffic management centers may use aggregated data that is collected from vehicles (speed, location, and trajectory) and stripped of identifying information to gain insights into congestion and road conditions as well. Communications links (such as fiber optic cables or wireless technologies) between roadside equipment and the local or state back office, private operator, or traffic management center. This is typically referred to as the “backhaul network.” Support functions, such as underlying technologies and processes to ensure that the data being transmitted are secure. DOT, state and local transportation agencies, academic researchers, and private sector stakeholders are engaged in a number of efforts to develop and test V2I technologies and applications, as well as to develop the technology and systems that enable V2I applications. DOT’s V2I work is funded through its connected vehicle research program. DOT’s initial connected vehicle research focused on V2I technologies; however, it shifted its focus to V2V technologies because they are projected to produce the majority of connected vehicle safety benefits and they do not require the same level of infrastructure investment as V2I technologies. After conducting much of the research needed to inform its advanced notice of proposed rulemaking to require that vehicle manufacturers install V2V technologies in new passenger cars and light truck vehicles, DOT is now shifting its focus back to V2I technologies, and some of the technical work needed to develop V2V applications has also informed the development of V2I. A number of DOT agencies are involved with the development and deployment of V2I technologies. In addition, private companies have received contracts from DOT to develop the underlying concept of operations and technologies to support V2I applications, and auto manufacturers are collaborating with DOT in its efforts to develop and pilot certain V2I applications and the underlying technologies to support them. State and local transportation agencies, which will ultimately be deploying V2I technologies on their roads, have also pursued efforts to test V2I technologies in real-world settings. However, to date, only small research deployments (such as those described below) have occurred to test V2I technologies: The Safety Pilot Model Deployment: DOT partnered with the University of Michigan Transportation Research Institute to collect data to help estimate the effectiveness of connected vehicle technologies and their benefits in real-world situations. The pilot was conducted in Ann Arbor, Michigan, from August 2012 to February 2014, and included roughly 2,800 V2V-equipped cars, trucks, and buses, as well as roadside V2I equipment placed at 21 intersections, three curve-warning areas, and five freeway sites. While the primary focus was on V2V technologies, the pilot also evaluated V2I technology, such as Signal Phase and Timing (SPaT) technologies. DOT officials stated that it would be releasing six reports with findings from the Safety Pilot in mid to late 2015, although these reports will primarily focus on V2V applications. As of July 2015, DOT has released one report that included an evaluation of how transit bus drivers responded to V2V and V2I warnings, and of how well the test applications performed in providing accurate warnings. The two V2I applications included were a curve speed warning and a warning that alerts the bus driver if pedestrians are in the intended path of the bus when it is turning at an intersection.