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SAE J2735-Draft-Rev28 [issued: 11-10-08]
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256 -
This is an SAE Motor Vehicle Council draft document of the DSRC committee, subject to change.
Annex C Operation with the Vehicle Basic Safe[RS3]ty Message
1.
Application Background
The message sets specified for vehicle safety (ACID 20) in this Standard were developed based on analysis
of communications requirements for seven high-priority vehicle-to-vehicle application scenarios with
significant anticipated safety benefits. These application scenarios are:
C.1
Intersection Collision Warning
C.2
Emergency Electronic Brake Lights
C.3
Pre-Crash Sensing
C.4
Cooperative Forward Collision Warning
C.5
Left Turn Assistant
C.6
Stop Sign Movement Assistance
C.7
Lane Change Warning
The use of the specified message sets in the relevant vehicle safety application scenarios is described in this
annex in Sections A-1 through A-7. These sections of the annex present vehicle safety application scenarios
and are meant to illustrate the use of the messages specified in this Standard, rather than to specify or
prescribe these applications or to recommend the best way to deploy these applications. It is expected that
these same message sets will fully or partially enable additional vehicle safety applications to be developed.
As these additional applications are developed, those illustrations may be added in additional sections to
this annex in future versions of this Standard.
Other future vehicle safety applications that are expected to be developed may require additional message
sets, data frames and data elements that have not yet been specified in this Standard. The intention of the
DSRC Technical Committee is for these additional elements to be identified by the technical committee,
analyzed, specified and added to future versions of this Standard in order to support interoperability for an
increasingly diverse range of vehicle safety applications. These additions are likely to be especially
noticeable in the area of future vehicle-to/from-infrastructure safety applications that are envisioned. Some
of these will likely be vehicle safety applications (ACID 20) and others are likely to be public safety
applications (ACID 19). The technical committee intends for this Standard to support the interoperability of
all these safety applications between and among vehicles from different manufacturers and roadside
infrastructure operators/manufacturers throughout the entire region of expected vehicle travel.
The basic premise of the initial vehicle safety applications is the use of frequent broadcasts of basic
information about each individual vehicle to enhance the awareness of vehicles that are in the vicinity. The
frequency of these broadcasts is expected to meet the requirements of vehicle safety systems implemented
using this technology. The frequency of of transmission above th[RS4]e application requirements is also
expected to generally compensate for the inherently unreliable nature of radio frequency communications.
Due to the potential cumulative effect of many vehicles broadcasting within the same local area (in
particular during heavy traffic conditions), the DSRC communication channel is likely to encounter
excessive channel loading. For this reason, it has been the focus of the technical committee to use a concise
selection of required information to include in these common messages and to provide effective coding to
minimize the size of the message payload for these repetitive messages. The common message set that was
developed by the committee to meet the requirements of the initial vehicle safety application scenarios was
therefore split into three parts:
MSG_BasicSafetyMessage Frame, Part I, which contains a fixed data structure comprising the information
that must be updated most frequently or which must be known to determine the meaning of the frequently-