Smart Traffic Synchronization Protocol (STSP) Version 1.0

This document defines the Smart Traffic Synchronization Protocol (STSP), version 1.0 -- an open, extensible protocol for real-time coordination of urban traffic signal infrastructure across distributed networks of intersections. STSP defines a standard message format, node state machine, synchronization algorithm, and inter-node communication model that enables any compliant traffic controller to participate in a federated intelligent network -- regardless of manufacturer, city, or country of deployment. The key contribution of STSP is the definition of the Infrastructure- to-Infrastructure (I2I) coordination layer -- a communication model between traffic signal nodes that does not exist as an open standard in any currently published specification. Existing standards such as SAE J2735 SPaT/MAP and ETSI ITS-G5 address Vehicle-to-Infrastructure (V2I) communication. STSP addresses the orthogonal problem: how nodes coordinate with each other. This document is placed in the public domain under CC BY 4.0 with Open Implementation Clause. Any city, government, company, or individual may implement STSP freely, provided that original authorship is attributed in all implementations, documentation, and derivative works as follows: "Implements STSP, designed by Gustavo Angel Aldana Flores (draft-aldana-stsp)."