ISO 21219-17:2023

Overview

ISO 21219-17:2023 - TPEG2-SPI (Speed information) is part of the ISO 21219 series for TPEG Generation 2 and defines the TPEG Speed Information (SPI) application used to report speed limits and speed-related data to travellers and vehicle systems. The standard specifies a compact, bandwidth-efficient encoding for delivering current speed limits - including static, variable and temporary signs - and supports differentiation by lane and vehicle type. It delivers timely speed data to navigation, driver assistance and telematics systems so drivers and automated systems can be aware of current permitted (maximum) speeds.

Key topics and technical requirements

• Scope and purpose: Reporting speed information for travellers; supporting both static and dynamic speed signage (e.g., variable message signs, temporary roadworks limits).
• Message structure: Defines SPI message components (SpeedInformationMessage, SpeedInformation, MMCSwitch, links for message management and location referencing).
• Data modelling: SPI datatypes (e.g., LaneNumber, SpeedLimitSegment) and enumerations/tables (SpeedInformationType, Context, VehicleType, InformationUnit).
• Direct vs. indirect limits:
  • Direct speed limits - explicit maximum speeds shown by signs (static or dynamic).
  • Indirect speed limits - inferred limits referencing other road users (e.g., vehicle in front).
• Location referencing: Integrates with TPEG2 location referencing options to map speed data to precise positions and lanes.
• Physical formats: Conversion rules for binary and XML (tpegML) representations are included in normative annexes to enable interoperable distribution.
• Compact encoding & bandwidth efficiency: Designed to minimize data size for broadcast and mobile networks.
• Extensibility and versioning: Application identification, version signalling and ordered components to support evolution and interoperability.

Practical applications and who uses it

• Navigation system vendors - integrate up-to-date speed limits (including temporary or dynamic changes) into route guidance and map updates.
• Automotive OEMs & ADAS developers - feed current speed limits to driver assistance systems (speed warnings, adaptive cruise control).
• Telematics & fleet operators - enforce compliance, manage speed-related alerts and improve driver safety.
• Traffic management centers & ITS service providers - broadcast dynamic speed regulations and temporary restrictions to road users.
• Map data providers - augment static map databases with live speed updates for lane- and vehicle-specific limits.

Benefits include improved road safety through timely awareness of legal speed limits, better support for dynamic traffic control, and efficient use of bandwidth for large-scale distribution.

Related standards

• ISO 21219-1 (TPEG2-INV) - introduction, numbering and versions
• ISO 21219-3 / -4 - UML-to-binary and UML-to-XML conversion rules
• ISO 21219-5 (Service framework), ISO 21219-6 (Message management container)
• Location referencing parts in the TPEG2 family (e.g., ISO/TS 21219-7 and related TLR/DLR/GLR parts)

Keywords: ISO 21219-17, TPEG2-SPI, TPEG Speed information, intelligent transport systems, speed limit information, variable message signs, navigation systems, driver assistance, compact encoding.