 |
 |
 |
 |
|
 |
 |
SAE J2735-Draft-Rev18 [issued: 06-26-07]
-
184 -
This is an SAE Motor Vehicle Council draft document of the DSRC committee, subject to change.
The message sender needs to have an algorithm to decide if an “emergency braking” message delivery is
necessary (for example: deceleration greater than 0.6g). If a vehicle determines that it is braking hard then
it could use the On-Board Unit of DSRC to share that information with others. The sending vehicle could
use the MSG_BasicSafetyMessageFrame, Part I and MSG_BasicSafetyMessageFrame, Part II messages to
issue this warning through the use of a higher priority level than the routine broadcast of
MSG_BasicSafetyMessageFrame, Part I and MSG_BasicSafetyMessageFrame, Part II.
In order to determine if an “emergency braking” message is relevant to the listening vehicle, the listening
vehicle needs to know the relative location from which the message originated (e.g., front, rear, left, right).
This can be done based on its GPS information and the GPS information of the braking vehicle. In this
simple near-term application scenario, an “emergency braking” message from a vehicle may not
necessarily apply to a vehicle traveling in an adjacent lane.
Sensors and Other System Needs
A map database, where available, may help to provide specific, relevant information related to current road
segments. This could allow, for example, intersection geometry or road curvature to be taken into account
when an application host vehicle evaluates “emergency braking message” to see if an alert to the driver is
necessary.