4-12. Connected Vehicle Traveler Information Message Guidelines.pdf

Traveler Information Message Guidelines

Overview These guidelines provide definitions for generating standardized Connected Vehicle Traveler Information Messages (TIMs). The intent of this guidance is to support Infrastructure Owner Operators (IOOs) in developing their TIM generation systems with the goal of providing consistent messaging to the driver/vehicles operating across the United States roadway network.

This TIM guide provides operational guidance related to multiple service packages defined in the National ITS Reference Architecture (ARC-IT) . Many of the ARC-IT service packages include “driver information” and/or “vehicle signage data” information flows. This TIM generation guidance directly supports these information flows by providing clear definitions for specific messages to be delivered to drivers and vehicles. These common definitions allow all parties to correctly interpret messages and relate them to roadway events and conditions.

Within this guide some TIM elements are rigorously defined to ensure that all consumers can unambiguously interpret the message. Other elements are more loosely defined to allow flexibility across IOOs regarding how and when they generate a given TIM. Each TIM definition includes four sections:

Conditions – This section roughly describes the conditions that would prompt the generation of a given TIM. Responsible IOOs will likely want to refine these condition descriptions to more closely align with their operations. The conditions may also describe constraints when a particular TIM should not be used.

Message – This section defines the exact International Traveler Information Systems (ITIS) phrases to apply for each TIM. The phrases identified for each TIM should not be altered. Using a consistent message phrase for each TIM is critical, as it enables unambiguous interpretation of each message. Some messages have parameters as part of the message phrase, allowing variable values to be incorporated into the message, for example a numeric value for a speed limit.

A “suggested driver display icon” is also included in the message section for each TIM. These display icons, based on MUTCD signage, are considered the fastest way for drivers to visually comprehend a TIM. Many of the icons are exact replicas of MUTCD signage, others follow the MUTCD color and shape conventions for different types of signage. These are suggested visual displays for the driver; on-board systems that provide visual displays for driver alerts may develop other more effective visual representations.

Geofence Extent – This section defines how the geofence, indicating the “area of relevance” of a given TIM, should be constructed. This area of relevance is where the IOO has determined that the message is highly relevant for drivers/vehicles on the roadway. Some elements of the geofence are flexible and may be determined by individual IOO operational rules, however there are geofence elements that are very tightly constrained to ensure a common understanding of roadway locations associated with the message.

Timing – This section describes constraints that may apply to the start and end times of a given TIM. For example, the end-time of a road construction TIM must accurately match the time when the associated road work is complete, and the work zone cleared from the roadway.

Assumptions This document makes several assumptions about the roles and responsibilities of the IOOs and the vehicle on-board systems.

● The IOO cannot control and does not intend to dictate how the data provided in the TIMs are used. The IOO does not assume responsibility for how the data is interpreted or acted upon.

● In-vehicle alerts may be visual, auditory, haptic, or any combination of the three. The nature of the alert may vary based on the vehicle make and model, driver-controlled settings, or the alert type.

● The content, timing, and delivery location of the TIMs from the IOO are intended to elicit device reactions, resulting in consistent driver information across IOO boundaries.

● The TIMs will adhere to data quality checks currently being developed by the industry. This will help ensure the accuracy and timeliness of the data provided to the vehicle.

● IOO deployment of TIMs may be performed by the IOO, may be integrated into construction contracts as an obligation of the contractor, or may be delegated by the IOO to a third party.

For the purposes of this document, the IOO is assumed to have final authority over messages created on their behalf.

● Messages may be sent via RSU, from a cloud-based service, over a cellular data connection, via satellite, or by other means of wireless communications. Different delivery methods may be used in different locations; different delivery methods may or may not be available for the same location.

● The messages may be consumed by third-party navigation systems, interpreted, and processed into customized navigation/travel updates. Subscribers to the third-party navigation systems may then receive navigation/travel updates that incorporate data from multiple TIMs but do not necessarily contain the exact information from each TIM.

● Messages may be intermittently unavailable due to maintenance or unplanned outages. If the TIMs are not available, drivers should rely on existing roadway communication means, such as roadside signage, dynamic message signs, and traffic control devices.

● All TIMs include location information, typically a geofence extent that defines the area of relevance for the TIM. This information will allow in-vehicle calculations regarding the vehicle location relative to the event location of the indicated warning. The geofence extent will vary depending on the TIM and is described in each TIM definition.

● The TIM source will be authenticated using the appropriate authentication mechanism for the selected message delivery method. For direct V2I delivery, this would entail the use of the SCMS to sign the message.

● TIMs in this document were designed to work with vehicle on-board systems with a Level 1 message receiver capability (See On-Board Message Receiver Capability section.)

On-Board Message Receiver Capability An important consideration in defining a TIM is the capability of the vehicle on-board systems to interpret and use the message information. To better qualify this concept, three levels of on-board systems capability were defined. These levels outline the different capabilities of on-board systems to use the messages. The different capability levels have different implications for generating TIMs, these considerations are outlined for each capability level.

Most CV On-Board Units (OBU) available in 2025 are at Level 1 capability. There may be some that implement one or two of the Level 2 capabilities, but no currently available OBUs reach the level 3 capability. However, delivery through third-party navigation systems may provide some level 3 capabilities. For example, if a third-party system identifies a road closed TIM, they may use this information to generate new routes to navigate around the road closure and deliver those new navigation plans to their affected subscribers. These on-board system capability levels are separate from the automated driving systems (ADS) capability definitions in SAE J3016. However, the on-board receiver capability Level 3 defined here implies integration of the TIM data with higher level ADS.

L e v e l

Name Function Description Considerations Generating TIMs

1 Basic Message Processing

● Reads content, location, and timing from TIM.

● Provides a driver alert when the vehicle is located within the defined geofence, vehicle heading is within defined bounds, and time is within defined active time.

● Alerts with the information found in the message content (per ITIS codes.)

● The number of simultaneous messages delivered within an area must be considered to avoid driver alert overload.

● Upstream geofence extents must be defined considering advanced warning time for drivers.

2 Enhanced Message Processing

● Reads content, location, and timing from TIM.

● Generally, provides a driver alert per the TIM defined geofence, but may adjust the alert area considering vehicle specific information such as speed.

● Active time of the TIM is always respected.

● The number of simultaneous messages delivered within an area must be considered to avoid driver alert overload.

● Upstream geofence extents must be defined considering advanced warning time for drivers.

● Provides a driver alert based on the content of the message but potentially altering the alert for better relevance for the vehicle/driver (e.g. adding distance countdown, not showing a reduced speed if driver is already at or below TIM speed limit, or not showing a TIM that is restricted to a different vehicle class than the host.)

● May implement smart alert filtering to avoid overloading driver with multiple simultaneous alerts.

3 Vehicle Integrated Message Processing

● Reads content, location, and timing from TIM.

● May use the TIM to generate a driver alert, and/or the data may be input to ADS for vehicle operation and navigation.

● TIM defined geofence primarily provides location data for the defined event. If a driver alert is generated, the geofence may be used to indicate where to provide a driver alert although the alert area may be modified based on vehicle specific data.

● Determines type of alert to deliver to the vehicle/driver, based on the content of the message but potentially altering the alert for better relevance for the vehicle/driver.

● Accuracy of location and timing information is more critical as it is used by

ADS.

● Geofences can be focused on the roadway event location, as on-board calculations will determine advanced alert distances if necessary.

Acronyms ADS Automated Driving System. See the SAE J3016 standard: Taxonomy and

Definitions for Terms Related to Driving Automation Systems for On-Road Motor Vehicles.

IOO Infrastructure Owner Operator ITIS International Traveler Information Systems – phrases commonly used in the transportation industry for describing traffic-related events of interest to travelers. See the SAE J2540 standard.

MUTCD Manual on Uniform Traffic Control Devices OBU On-Board Unit – refers to a general class of devices/applications in or integrated with a vehicle which can receive TIMs and use these messages to support the safe operation of the vehicle by informing the driver or providing input to automated driving systems.

SCMS Security Credential Management System TIM Traveler Information Message – a standard connected vehicle message type to deliver roadway advisory and regulatory information to equipped vehicles. See the SAE J2735 standard.

TTC Temporary Traffic Control – refers to traffic control devices used to control traffic flow for non-permanent roadway changes. Cones, barriers and arrow boards are all examples of TTC devices.