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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 Functional Requirements document is intended for use by those agencies accepting the SPaT Challenge as they prepare for their deployments.
3. Document Overview
This document 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 companion document to this is the Model Concept of Operations document, which 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 intent of these documents is to be utilized by state, city, and county Departments of Transportation (DOTs) as they begin to plan their SPaT Challenge deployment. This Model Functional Requirements 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 Functional Requirements to address local specific needs. Further, this document contains 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. The accompanying Model Concept of Operations contains additional introductory and system information that will aid readers in understanding the system and functional requirements presented below.
4. Functional Requirements Organization
The SPaT Infrastructure Functional Requirements are organized within 12 functional groups:
- Group 1: Manage Interface to SPaT Sources requirements that describe the functions of the SPaT Infrastructure System to interface with sources of SPaT data.
- Group 2: Manage SPaT requirements that describe the functions of the SPaT Infrastructure to assemble the SPaT data into standard SPaT messages for broadcast.
- Group 3: Manage User Interface requirements that describe the functions of the SPaT Infrastructure System User Interface to manage functions of the SPaT Infrastructure System.
- Group 4: Manage Maps requirements that describe the functions of the SPaT Infrastructure to manage MAP data, use the correct MAP data for conditions and assemble standard MAP messages.
- Group 5: Manage Position Correction requirements that describe the functions of the SPaT Infrastructure to obtain GPS correction data, configure the source of correction data and assemble standard GPS correction messages.
- Group 6: Manage SPaT Vehicle System Interface requirements that describe the functions of the SPaT Infrastructure to broadcast and receive standard messages to/from SPaT Vehicle Systems.
- Group 7: Manage Preemption / Priority requirements that describe the functions of the SPaT Infrastructure to monitor requests for preemption and priority, manage conflicting requests, generate requests from and responses to SPaT Vehicle Systems.
- Group 8: Manage Vehicle & PID Data requirements that describe the functions of the SPaT Infrastructure to manage data received from vehicles and PIDs
- Group 9: Manage Traffic Data System Interface requirements that describe the functions of the SPaT Infrastructure System to exchange data with the Traffic Data System.
- Group 10: Manage Security requirements that describe the functions of the SPaT Infrastructure to obtain and send security credentials, verify the credentials received and use that information to manage network access.
- Group 11: Manage Security Back End Interface requirements that describe the functions of the SPaT Infrastructure to enable Traffic Engineering staff to configure the security interface.
- Group 12: Provide Support requirements that describe the functions of the SPaT Infrastructure to provide support to users to monitor status, activity and configure the system.