Connected Intersection (CI) Phase 2

USDOT and ITE have worked on ITS standards since the inception of the ITS Standards Program over last couple of decades. The USDOT, in conjunction with ITE, SAE International (SAE), the American Association of State Highway and Transportation Officials (AASHTO), the National Electrical Manufacturers Association (NEMA), and early deployment agencies, successfully developed a Connected Transportation Interoperability (CTI) 4501 Connected Intersections Implementation Guide under an equal equity voting membership between the traditional automotive stakeholder community led by SAE and the traditional Intelligent Transportation Systems (ITS) infrastructure community stakeholders led by ITE, AASHTO and NEMA. CTI 4501 provided the deployment guidance and concepts necessary to help deploy nationally interoperable CI applications. During the course of development and validation of CTI 4501, a number of potential activities were identified to update and enhance the existing guidance moving forward, initially identified as CI Phase 2 effort.


CTI 4501 v02 CI Implementation Guide

The Connected Intersection (CI) Implementation Guide is developed by engaging with stakeholders representing the industry at large including but not limited to infrastructure owners/operators (IOOs), automobile original equipment manufacturers (OEMs), roadside unit (RSU) manufacturers, and the end users of data and services. The work is supported by the United States Department of Transportation (USDOT) Intelligent Transportation Systems (ITS) Joint Program Office (JPO). Several associations such as the American Association of State Highway Transportation Officials (AASHTO), the Institute of Transportation Engineers (ITE), the National Electrical Manufacturers Associations (NEMA), and SAE International are involved in ensuring a balanced and effective stakeholder representation and adherence to standards development processes as Standards Development Organizations (SDOs).



This CI Implementation Guide addresses the ambiguities and gaps identified by early deployers and provides guidance to generate messages and develop applications for signalized intersections that are interoperable across the United States, especially for the automated transportation systems. This document focuses on harmonizing the existing signal phase and timing (SPaT) messages deployed, using the USDOT sponsored Cooperative Automated Transportation Clarifications for Consistent Implementations (CCIs) To Ensure National Interoperability Connected Signalized Intersections as a starting point.

This Guide defines procurement and implementation guidance and the expectations leading to minimum performance requirements for a connected intersection. It is intended to be used by IOOs to provide guidance on how to implement an interoperable connected intersection. For OEMs and other application developers, this document provides an explanation on what data and connected vehicle messages are being provided from an interoperable connected intersection so safety applications can be developed for production vehicles, with an initial focus on the Red-Light Violation Warning application. The Needs to Requirements Traceability Matrix (NRTM) in Section 3.2.3 provides the guidance to IOOs for the procurement of a connected intersection.

The Guide follows a Systems Engineering Process (SEP), so the contents of this document include a Concept of Operations (ConOps), a System Requirements (Functional Requirements), and System Design Details sections. It also includes a Needs to Requirements Traceability Matrix (NRTM) and a Requirements Traceability Matrix (RTM). Users of this CI Implementation Guide should use the NRTM and RTM to determine how to design a connected intersection that satisfies their specific needs.

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Subject:              Connected Intersections (CI) Phase 2 Stakeholder

Version No.
Overall Status Under Development

Task 3

Balloting and Publication

Not Started



J3238/2 Draft Development

Not Started



J3238/1 Draft Development

Not Started


Task 2

Test Planning and Execution

Not Started



CTI 4501 Recommended Standard

Not Started



System Design Details (SDD)

Not Started



System Requirement Specification (SRS)

Under Development


CTI 4501 v02

Concept of Operations (ConOps)



Task 1

CTI 4501 Draft Development

Under Development



Project Management Plan (PMP)








Period of Performance (POP)


9/12/22- 9/11/24