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SAE J2735-Draft-Rev18 [issued: 06-26-07]
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179 -
This is an SAE Motor Vehicle Council draft document of the DSRC committee, subject to change.
new random value to ensure the overall anonymity of the vehicle. Because this value is used as a means to
identify the local vehicles that are interacting during an encounter, it is used in the message set.
Annex A Operation with the Vehicle Safety Message
1.
Application Background
The message sets specified for vehicle safety (ACID 20) in this Recommended Practice 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:
Intersection Collision Warning
Emergency Electronic Brake Lights
Pre-Crash Sensing
Cooperative Forward Collision Warning
Left Turn Assistant
Stop Sign Movement Assistance
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 Recommended Practice, rather than to
specify or prescribe these applications or to recommend the best way to deploy these applications. It is
expected that these same initial 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 Recommended Practice.
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 Recommended Practice. 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 Recommended Practice 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
Recommended Practice 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 transmission above the application requirements is also expected to
generally compensate for the inherently unreliable nature of radio frequency communications.
Although the bandwidth available within a DSRC channel at any given point is at least 3 Mbps, and the
default transmission rate is 6 Mbps, the net cumulative effect of many vehicles broadcasting within the