Terminology & Glossary

5G Cellular

Fifth-generation wireless or 5G is the newest mobile network for cellular communication. It is replacing the current 4G-LTE technology by providing a number of improvements in speed, coverage, and reliability. When fully mature, 5G will revolutionize our ability to stream data on our phones and will facilitate the “internet of things”, where a broad variety of devices are connected. 5G systems will eventually be installed in vehicles to provide telematics services, much like 4G is today. These services will include navigation aids, software updates, music and movie streaming, and other infotainment systems. These services will continue to be subscription based; vehicle owners will pay a fee for this information.

Advanced Driver Assistance Systems (ADAS)

Electronic systems that help the vehicle driver during driving functions. Examples include lane departure warning systems, automatic lane centering, cruise control, electronic stability control and automatic emergency braking. ADAS usually rely on imaging and sensor technologies. These features differ from automated driving systems in that they typically do not relieve the driver from driving, but simply assist while the driver continues to operate the vehicle.

Automated Driving System (ADS)

The hardware and software that are collectively capable of performing all driving tasks on a sustained basis. These driving tasks may be limited to certain conditions or geographic constraints. This term is the correct technical term, as specified by the Society of Automotive Engineers, for systems that render a vehicle “automated”, “autonomous” or “driverless”.

Automated Vehicle (AV)

Vehicles that have some automated features but are not completely autonomous. Using the same on-board sensor technology as in autonomous vehicles, these vehicles can take over some, but not all, of the driving function of the human driver. The driver still needs to be available to monitor and/or take over other driving functions. Many newer automobiles have automated features. The Society of Automotive Engineers have defined six levels of automation, with each level having a different degree of automated capability.

Autonomous Vehicle

A vehicle that uses radar, lidar, cameras, GPS, odometry, artificial intelligence and other hardware and software to control, navigate, and drive the vehicle without direct human input. These are sometimes referred to as self-driving vehicles, driverless vehicles, or robotic vehicles. The terms “autonomous” and “automated” are sometimes used interchangeably, but there are subtle differences. “Autonomous” means “self governing, without external intervention”. Vehicles that are fully autonomous are not available yet.

Basic Safety Message (BSM)

A standardized, digital packet of data used in connected vehicle systems that contains the vehicle position, heading, speed, and other information relating to a vehicle’s state and predicted path. The BSM contains no personally identifying information (PII). The BSM is typically broadcast by a vehicle on-board unit ten times per second. It is used in V2V and V2I applications to prevent crashes and improve mobility.

Cellular Vehicle-to-Everything (C-V2X)

C-V2X is a cellular technology that facilitates very fast communication of critical data between a connected vehicle and connected infrastructure. It is based on 4G-LTE cellular technology, but uses the 5.9GHz spectrum and communicates directly between devices, not through a cell tower. C-V2X is not the same as 5G. C-V2X has been developed in recent years, and is deployed in only a few locations at this time, with limited evaluation of its capabilities. UDOT has deployed and tested this technology.

Connected and Automated Vehicle (CAV)

Vehicles that have the features of both a connected vehicle and an automated vehicle. Some vehicles will be connected but not automated, others will be automated but not connected, and some will have both capabilities. Connected vehicle capabilities and automated vehicle features are complimentary.

Connected Vehicle (CV)

A technology that allows vehicles to wirelessly communicate with each other, connected infrastructure (like traffic signals) and other travelers. The data sent from connected vehicles is anonymous. This data can help drivers avoid crashes and enable transportation agencies to improve mobility and reduce congestion. Connected vehicle systems can involve vehicle-to-vehicle (V2V) or vehicle-to-infrastructure (V2I) communication. Vehicles may also communicate to other travelers, like pedestrians or bicyclists, sometimes referred to as vehicle-to-pedestrian (V2P) communication. The combined capability of these modes is often referred to as vehicle-to-everything (V2X). Connected vehicles use DSRC or C-V2X communication technologies.

Cooperative Automated Transportation (CAT)

Using technology, including connected vehicle technology, automated driving systems, mobility as a service networks, intelligent transportation systems and integrated trip planning to encourage all modes of transportation to work in concert to provide travelers a safe, reliable, sustainable, and integrated transportation experience. The term “cooperative” implies interdependence.

Curve Speed Warning

Curve speed warning systems use V2I communication to send warnings to vehicles about upcoming curves in the roadway. The system evaluates the geometry of the curve and the speed of the vehicle to determine the nature of the warning message. UDOT is planning to implement this V2I warning system at various roadway curves that have high numbers of crashes.

Data Ecosystem

A tiered data environment with managed access for software developers and partners to provide innovative transportation solutions. Messages sent back and forth between vehicles, infrastructure, and other travelers in a connected vehicle environment will be stored in this data ecosystem. The UDOT Data Ecosystem will be cloud-hosted and is being developed in a partnership agreement with Panasonic of North America. Also referred to as a V2X Data Ecosystem (VDE).

Dedicated Short Range Communication (DSRC)

DSRC is a wireless communication system, much like wifi, that operates on the 5.9GHz radio frequency spectrum. It was designed specifically to allow connected vehicles to communicate with connected infrastructure through on-board and roadside equipment. It has very low latency (high speed) and does not require a subscription fee. It has been broadly deployed and tested.

Driverless Vehicle

See “Autonomous Vehicle”.

Distributed Acoustic Sensing (DAS)

Distributed Acoustic Sensing is a technology that uses fiber optic cable to detect and report vibrations in the ground along the path of the fiber. These vibrations might be caused by moving vehicles, vehicle crashes, or other incidents, such as an avalanche. The system is capable of classifying the cause of the vibration and reporting it within a few feet of its location.

Intelligent Transportation Systems (ITS)

A combination of information and communication technologies used in transportation and traffic management systems to improve the safety, efficiency, and sustainability of transportation networks, to reduce traffic congestion and to enhance drivers’ experiences. Common elements of an ITS system are traffic cameras, electronic message signs, sensors to measure traffic volumes and speeds, and fiber optic communication systems. Connected vehicle technology is a recent addition to some ITS systems.


Light Detection and Ranging, a method for measuring distances using laser light. Aggregating many points of data measured using LiDAR creates a 3-dimensional representation of objects. Many automated driving systems use LiDAR to map the real-time environment around the vehicle.

Low Latency

Latency is a measure of delay. In computer networks or wireless communication, latency is the measurement of the delay that occurs from sending a message to receipt of that message. For connected vehicles to send and receive messages to effectively prevent crashes between moving vehicles, the latency must be very small. This low latency requirement is generally considered to be less than 20 milliseconds, or two hundredths of a second.

MAP Message

A standardized, digital packet of data used in connected vehicle systems that describes the geometry of a roadway or intersection, including number and width of traffic lanes, locations of crosswalks, and configuration of turning lanes. The MAP message is broadcast by a roadside unit alongside the roadway once every second. It is used in V2V and V2I applications to prevent crashes and improve mobility.

Multi-modal Intelligent Traffic Signal System (MMITSS)

A software system which utilizes vehicle-to-infrastructure communication to consider and balance signal priority requests from multiple vehicles approaching a traffic signal. MMITSS was originally developed at the University of Arizona for the Connected Vehicle Pooled Fund Study. UDOT modified the original MMITSS system to create the TSP and Signal Preemption systems used in Utah. The UDOT version of the software is referred to as MMITSS-Utah

On-board Equipment (OBE)

Equipment installed inside vehicles that transmits and receives data between vehicles and the infrastructure using V2X technology. Also referred to as on-board units (OBU).

Roadside Equipment (RSE)

Equipment installed in infrastructure along a road or pedestrian pathway that transmits and receives data to and from vehicles using V2X technology. Also referred to as roadside units (RSU).

Road Weather Information System (RWIS)

An installation of environmental sensors used to assess weather conditions. The sensors measure temperature, wind speed, precipitation, pavement temperature, and other local conditions. The UDOT RWIS stations are positioned along roadways throughout Utah and transmit real-time conditions data to meteorologists at the Traffic Operations Center.

Security Credential Management Systems (SCMS)

A system used to secure V2X messages from misuse and enable secure, authentic and private communications. In a V2X system, a digital credential is attached to each wireless message sent between vehicles, the roadside infrastructure, and other travelers. These digital credentials are provided by a third-party and are authenticated by a secure private key. This system is similar to security methods used to secure credit card and other financial transactions over wireless networks.

Signal Preemption

A signal preemption system interrupts traffic signal timing to allow critical vehicles to pass through the intersection without stopping. Usually used for emergency vehicles, the signal is turned green when requested by the vehicle, and conflicting traffic is prevented from crossing the intersection. Using roadside and on-board V2I technology, UDOT provides signal priority to its snow plows on certain corridors when they are actively plowing. Using other types of technology, some cities provide preemption to emergency vehicles.

Signal Request Message (SRM)

In a transit signal priority or signal preemption system, the vehicle on-board unit broadcasts a standardized, digital SRM to the roadside unit to request signal priority or preemption at a traffic light.

Signal Request Message (SRM)

In a transit signal priority or signal preemption system, the vehicle on-board unit broadcasts a standardized, digital SRM to the roadside unit to request signal priority or preemption at a traffic light.

Signal Status Message (SSM)

In a transit signal priority or signal preemption system, the roadside unit broadcasts a standardized, digital SSM to confirm the receipt of an SRM received from the vehicle on-board unit.

Spot Weather Impact Warning

Spot weather impact warnings use V2I communication to send location-specific weather warnings directly to drivers as they approach adverse road conditions like ice or fog. Sensors installed along the road, and information gleaned from previous vehicles, provide the information needed to determine the nature of the warning message. Providing specific warnings at roadway segments with high rates of weather-related crashes will reduce these crash rates.

Traffic Operations Center (TOC)

The TOC is the nerve center of all traffic information for the Utah Department of Transportation. Using advanced technologies such as cameras and traffic and weather sensors, operators in the TOC can monitor traffic, detect accidents/problems and take actions necessary to mitigate impacts and return traffic flow to normal.

Transit Signal Priority System (TSP)

A TSP system modifies traffic signal timing and gives priority to selected vehicles at signalized intersections that are equipped with appropriate technology. The signal is asked to stay green, or initiate green earlier, to allow more time for the selected vehicle to pass through the intersection. Using roadside and on-board V2I technology, UDOT provides signal priority to Utah Transit Authority (UTA) buses on certain corridors, when they are running late, to help them get back on schedule. TSP systems reduce transit delay and improve transit reliability.

Vehicle-to-everything (V2X)

A system where vehicles share and receive information with other vehicles, other travelers, and the infrastructure using low-latency, wireless communication technology. It includes V2V and V2I systems. Today, the technologies used for V2X communication include DSRC and C-V2X systems.

Vehicle-to-Infrastructure (V2I) Communication

V2I technology enables vehicles to share and receive information with roadside units using low latency, wireless communication technology. Today, those technologies include DSRC and C-V2X systems. Information communicated through V2I technology is intended to prevent crashes and improve traffic mobility by providing useful information to the driver, the vehicle systems, the infrastructure and roadway operators.

Vehicle-to-vehicle (V2V) Communication

The capability of vehicles to wirelessly communicate with other vehicles using low-latency technology. Information shared between vehicles through V2V technology is intended to prevent crashes by warning drivers of impending danger, such as an oncoming vehicle that can’t be seen.

Work Zone Warning

Work zone warnings use V2I communication to send real-time information to vehicles about upcoming work zones. Information can include lane obstructions, closures, lane shifts, speed reductions, worker presence, etc.