ISO/TS 20684-3:2022

Overview

ISO/TS 20684-3:2022 - "Intelligent transport systems - Roadside modules SNMP data interface - Part 3: Triggers" defines standardized mechanisms for firing triggers on ITS field devices so those devices can initiate actions. It is part of the ISO 20684 series that specifies SNMP-based management information for roadside modules and field devices such as traffic signals, variable message signs, weather stations, traffic sensors, and C‑ITS roadside equipment. The document focuses on the needs, requirements and design for trigger mechanisms that prompt actions (e.g., notifications, logging, SNMP requests), and it provides MIB definitions and a requirements traceability matrix.

Key Topics

• Trigger types
  • Schedule triggers - time/date driven triggers and associated day plans and schedulers.
  • Schedule day plans - reusable day definitions mapped to schedules.
  • Condition-based triggers - triggers based on monitored data values and events (including hysteresis behavior).
• Action manager - central entity that coordinates trigger-initiated actions; includes configuration, capability discovery, enable/disable, statistics and lifecycle operations.
• Data exchange and conformance - SNMP management information base (MIB) definitions (Annex A), SMIv2 conventions, and conformance mappings to user needs and requirements (Annex B).
• Capability and configuration requirements - device capabilities discovery, trigger creation/configuration/deletion, status monitoring, statistics retrieval and enable/disable controls.
• Security considerations - identification of security vulnerabilities associated with triggers and management operations.
• Standards alignment - designed to work with ISO 20684-1 overview, other ISO 20684 parts (e.g., Part 4 notifications, Part 5 logging, Part 6 SNMP requests, Part 7 support features) and SNMP RFCs.

Applications

ISO/TS 20684-3:2022 is intended for:

• Device manufacturers implementing SNMP interfaces for ITS field devices.
• Traffic management agencies and system integrators specifying interoperable roadside equipment.
• ITS software developers building management stations that configure and monitor triggers and actions.
• Procurement teams seeking open, non‑proprietary specifications for field device interoperability.

Practical uses include scheduled message updates on VMS, automatic event logging when sensors cross thresholds, or condition-triggered notifications for maintenance and alarms. The specification promotes reduced deployment time, easier integration, and improved maintainability through standardized SNMP data interfaces.

Related Standards

• ISO/TS 20684-1 (Overview)
• ISO/TS 20684-4 (Notifications), -5 (Logging), -6 (SNMP requests), -7 (Support features)
• IETF RFCs for SMIv2/SNMP (e.g., RFC 2578/2579/2580/3411)
• Notes: the document highlights similarities with NTCIP 1103 and 1201 where applicable.

Keywords: ISO/TS 20684-3:2022, intelligent transport systems, SNMP, triggers, roadside modules, field devices, action manager, conditional triggers, schedule day plans, MIB, ITS interoperability