Link Type: Field to Field

Roadside Equipment --> ITS Roadway Equipment:
signal preemption request


signal preemption request (Information Flow): Direct request for preemption to a traffic signal controller that results in preemption of the current control plan and grants right-of-way to the requesting vehicle. This flow identifies the required phase and timing of the preemption. This flow may also cancel the preemption request (e.g., when the requesting vehicle clears the intersection).

Roadside Equipment (Source Physical Object): 'Roadside Equipment' (RSE) represents the Connected Vehicle roadside devices that are used to send messages to, and receive messages from, nearby vehicles using Dedicated Short Range Communications (DSRC) or other alternative wireless communications technologies. Communications with adjacent field equipment and back office centers that monitor and control the RSE are also supported. This device operates from a fixed position and may be permanently deployed or a portable device that is located temporarily in the vicinity of a traffic incident, road construction, or a special event. It includes a processor, data storage, and communications capabilities that support secure communications with passing vehicles, other field equipment, and centers.

ITS Roadway Equipment (Destination Physical Object): 'ITS Roadway Equipment' represents the ITS equipment that is distributed on and along the roadway that monitors and controls traffic and monitors and manages the roadway itself. In CVRIA, this physical object represents all of the other ITS field equipment that interfaces with and supports the Connected Vehicle Roadside Equipment (RSE). This physical object includes traffic detectors, environmental sensors, traffic signals, highway advisory radios, dynamic message signs, CCTV cameras and video image processing systems, grade crossing warning systems, and ramp metering systems. Lane management systems and barrier systems that control access to transportation infrastructure such as roadways, bridges and tunnels are also included. This object also provides environmental monitoring including sensors that measure road conditions, surface weather, and vehicle emissions. Work zone systems including work zone surveillance, traffic control, driver warning, and work crew safety systems are also included.

Included In

This Information Flow is in the following Applications:

This Information Flow is in the following Application Objects:

Communication Diagrams

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This profile describes standards applicable to communications between roadside equipment and other field equipment such as traffic signal controllers that is represented by ITS Roadway Equipment in CVRIA.



Characteristic Value
Time Context Recent
Spatial Context Adjacent
Acknowledgement False
Cardinality Unicast
Initiator Source


This information flow triple is in the following applications with the following security levels.

Information Flow Security
Application Confidentiality Integrity Availability
Basis Basis Basis
Emergency Vehicle Preemption Not Applicable High Moderate
It does not matter if someone is able to eavesdrop on this request. There will be many other more obvious indicators that the request was made, such as sirens and flashing lights on the emergency vehicle. The system must be able to trust these requests. Emergency Vehicles should be able to send these requests and know that they are being operated on by the receiving system. Additionally, if an unauthorized vehicle is able to send these requests it could bring traffic to a standstill by disrupting signal coordination citywide. The alternative to this request is existing mechanisms – such as using the sirens to stop traffic. The difference between the emergency signal preemption application and existing practice is not significant enough to justify a HIGH availability requirement.