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SAE J2735-Draft-Rev29 [issued: 12-11-08]
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241 -
This is an SAE Motor Vehicle Council draft document of the DSRC committee, subject to change.
Sensors and Other System Needs
A map database could help to provide information about whether crossing path vehicles are in the vicinity
of an intersection. If lane resolution is possible, lane position of the crossing path vehicle can be used in
the algorithm, e.g., if a crossing path vehicle is in a left-turn pocket and it is known in advance that the left-
turn and straight-through phases are different, then the left-turning vehicle is no longer a likely threat.
Annex C-2 Emergency Electronic Brake Lights
Application Description
When a vehicle brakes hard, the Emergency Electronic Brake Light application conveys this information to
surrounding vehicles via one or more Basic Safety Messages. This application will help the driver of a
following vehicle by giving an early notification that the lead vehicle is braking hard even when the
driver’s visibility is limited (e.g. a large truck blocks the driver’s view, heavy fog, rain).
The current brake lamp goes on when the driver applies the brake. The Emergency Electronic Brake Light
application might not only enhance the range of a hard braking message but also might provide important
information such as acceleration/deceleration rate and duration. At present, brake lamps do not differentiate
level of deceleration and are only useful as far rearward as line of sight allows.
Flow of Events
Flow of events
1. Vehicle “A” sends MSG_BasicSafetyMessage, possibly with additional data associated with
the hard braking event, such as a hard-braking event flag
2. Vehicle “B” receives message
3. Vehicle “B” processes the message from Vehicle A and determines that Vehicle A’s message
is relevant (similar heading in advance of Vehicle B’s path) and a significant braking event is
occurring per the message information (e.g. deceleration, brake pressure, event flag).
4. Vehicle “B” alerts its driver to the braking event and provides some indication of braking
severity.
Hardware Devices:
DSRC radio
Positional and vehicle sensors
Human-Machine Interface
Occupant
Vehicle
System
Driver
Passenger
Service
Provider
Road
Department
Actors: (What entities play an
active role in use)
X
X
Support information:
CAMP-VSC Task 3 Report, 2003