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SPaT Challenge Infrastructure System Model Concept of Operations

Download the SPaT Challenge Infrastructure System Model Concept of Operations Draft Version 1.6. (Updated: March 2018) | Click here

1. Background

The American Association of State Highway Transportation Officials (AASHTO), the Institute of Traffic Engineers (ITE), and ITS America (ITSA) working together through the Vehicle to Infrastructure Deployment Coalition (V2I DC) have challenged state and local public sector transportation infrastructure owners and operators (IOOs) to work together to achieve deployment of roadside Dedicated Short Range Communications (DSRC) 5.9 GHz broadcast radio infrastructure to broadcast signal phase and timing (SPaT) in real-time at signalized intersections on at least one road corridor or street network (approximately 20 signalized intersections) in each of the 50 states by January 2020. This is commonly called the SPaT Challenge. In 2017, the National Highway Traffic Safety Administration (NHTSA) released a notice of proposed rulemaking (NPRM) (inviting industry comments) that, if enacted, would require all new light vehicles sold in the US to be equipped with DSRC radios which can continuously and anonymously transmit basic information about the location, speed and critical operation of the vehicles. These radios may also be able to receive agency transmitted data, such as SPaT, with the intent to support safer, more efficient operations.

2. Purpose

While the primary goal of the SPaT Challenge is to deploy DSRC broadcasts of the SPaT messages, the long term objective is sustained operation of connected vehicle applications that utilize the SPaT messages. For this reason, agencies accepting the SPaT Challenge are encouraged to consider a systems engineering approach towards planning and implementing the SPaT Challenge. The initial steps in the systems engineering approach include development of a Concept of Operations (ConOps) document and related system requirements.
This Model Concept of Operations document is intended for use by those agencies accepting the SPaT Challenge as they prepare for their deployments.

3. Document Overview

This Model Concept of Operations document provides a summary of stakeholder groups, system types, stakeholder needs, and operational concepts that describe the sequence of operational events and activities carried out by each stakeholder group. The companion document to this is the SPaT Challenge Model Functional Requirements, in which model requirements are defined and traced back to the operational concepts and ultimately to the user needs.
The intent of this document is to be utilized by state, city, and county Departments of Transportation (DOTs) as they begin to plan their SPaT Challenge deployment. This Model Concept of Operations document is written to be circulated as a working draft, with the intent that readers will benefit from the text in the document as they prepare their own individual ConOps to address local specific needs. Further, the accompanying Functional Requirements contain industry input to define the minimal requirements that will be required to maintain compatibility between the SPaT messages being broadcast and the vehicle on-board units planned for deployment by the automobile industry.

4. Scope

SPaT is a supporting function that supports several V2I connected vehicle applications. This ConOps assumes that SPaT is being deployed to support applications such as Red Light Violation Warning (RLVW), Pedestrian in Signalized Crosswalk Warning, and Eco-Approach and Departure at Signalized Intersections (Eco A/D) within the vehicle. Additionally, SPaT deployments will support the Mobile Accessible Pedestrian Signal System (PED-SIG) application on a mobile Personal Information Device (PID). These applications are discussed throughout this ConOps. These applications generally have been more widely researched, documented, and deployed. Many other V2I connected vehicle applications may be developed and deployed locally that are closely related to SPaT broadcasts and, based on specifics of the local deployment, may use the SPaT data. Examples of these applications include Signal Priority (transit, freight, other fleet vehicles), Emergency Vehicle Preemption (PREEMPT), and Probe-enabled Traffic Monitoring. These other V2I connected vehicle applications are not addressed in this version of this document, but may be covered in updates to this model ConOps. 

5. System Boundary

The SPaT Infrastructure System exists in a larger context of other functional components that make up the SPaT Enabled V2I Connected Vehicle System. The main user of the SPaT applications is the vehicle driver. However, the vehicle driver does not interact directly with the SPaT Infrastructure System, but instead interacts with the SPaT Vehicle System and therefore is considered an ‘indirect user’. With the exception of the priority and preemption applications, transportation agencies are typically not the entities providing the SPaT Vehicle System. Therefore, from the point of view of the SPaT Infrastructure System, the SPaT Vehicle System, not the driver, is considered to be the user stakeholder for the in-vehicle applications. A second indirect user group is the pedestrians crossing the intersection, specifically the visually impaired or vulnerable pedestrians. Like the drivers, they will not interact with the SPaT Infrastructure System, but rather with Personal Information Devices (PIDs), typically hand-held devices that receive and transmit data and provide user information.
Other users of the SPaT Infrastructure System include the individuals and systems that will interact with the SPaT Infrastructure System in some way.