Traffic TPEG API Developer's Guide

Implementation details

The Traffic TPEG API is implemented according to the guidelines found in the Implementation Alternative-2 (Annex B) in TPEG over HTTP specification.

Supported TPEG applications

TEC (Traffic Event Compact). For details, see "Intelligent transport systems - Traffic and Travel Information (TTI) via Transport Protocol Experts Group, Generation 2 (TPEG2) - Part 15: Traffic Event Compact (TPEG2-TEC_3.2/002)".
TFP (Traffic Flow and Prediction). Real time traffic flow as FlowMatrix. For details, see "Intelligent transport systems (ITS) - Traffic and Travel Information (TTI) via Transport Protocol Experts Group, Generation 2 (TPEG2) – Part 18: Traffic Flow and Prediction application (TPEG2-TFP_1.0/003)".

Note: Versions of TEC/TFP not listed in these specifications are ignored.

Traffic TPEG API allows an application to use different IP addresses for initsession and getmessages requests.

For example, an OEM application could send an initsession request, and the in-car system could send further getmessages requests.

Supported location referencing

Selection between the following supported location referencing methods is based on traffic content, application type, and preference.

TMC - Traffic Message Channel location referencing. For details, see ISO 14819-1:2013 "Intelligent transport systems -- Traffic and travel information messages via traffic message coding -- Part 1: Coding protocol for Radio Data System -- Traffic Message Channel (RDS-TMC) using ALERT-C".
ETL - Extended TMC Locations referencing. For details, see "Intelligent transport systems (ITS) - Traffic and Travel Information (TTI) via Transport Protocol Experts Group, Generation 2 (TPEG2) – Part 20: Extended TMC Locations for applications (TPEG2-ETL_1.0/001)".
OLR - OpenLR Location Referencing. For details, see "Intelligent Transport Systems (ITS) — Traffic and Travel Information (TTI) via Transport Protocol Experts Group, Generation 2 (TPEG2) - Part 22: OpenLR location reference (TPEG2-OLR_1.0/002)".

Combinations of different Loc-Ref types

Combinations of different Loc-Ref types are allowed, with the following priority order:

ETL/TMC - ETL will be returned only in case of extended TMC info is available
XYLR - used for coding locations which are not TMC covered, but is supported only by internal implementation

Note: Location referencing methods not listed in these specifications are ignored.

TPEG2 toolkits

The Message Management Container (MMC) is used by all TPEG applications to provide information about the handling of messages on the TPEG client side. MMC Implementation supports Monolithic Message Management. Multipart Message Management is not supported. See "Intelligent transport systems (ITS) - Traffic and Travel Information (TTI) via Transport Protocol Experts Group, Generation 2 (TPEG2) – Part 6: Message Management Container (TPEG2-MMC_1.1/001)".

Session characteristics

TPEG-over-HTTP implementation alternative 2 uses sessions to identify applications. Session information is created by an InitSession request, then included in GetMessages requests.

Sessions are identified by the getmessages cfg parameter, which can be used instead of the Session ID.