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 Application 9: Accident Occurrence Warning


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Using this application the accident warning message will be sent to the vehicles approaching to the accident point. The warning message also will be transmitted to the RSUs in adjacency.  Therefore, the Central Control Room (CCR) can be notified about the crash and prepares and informs the rescue team or the police officers based on the crash severity.

figure 1: Accident Occurrence Warning

Basic assumptions:

1. Employing GPS for vehicles positioning.

2. The target vehicles have been categorized into two categories. First category includes the vehicles that are at the 300m away and at the back of the crashed vehicle and also are at the same direction this group is called the main target vehicles. Second group includes the vehicles that are 300-600m away from the back of the crashed vehicle and are at the same direction this group is called the secondary target vehicles group.

3. We assume that the system assists those drivers that do not have the straight vision of the crashed vehicle and are at the same direction with the crashed vehicle and also are at about 600m away from it and at the back of it (although the information has been broadcasted).

4. We assume these parameters in order to determine the non-escaping distance, speed = 120km/h(33m/s) , brake acceleration=-6.5 m/s2 and the average speed of reaction=0.7sec:

Non-escaping distance= 85.3+23.3=108.6m,

the defined distance prior to the reaction= 33.3*0.7=23.3m, and

the red line length= 85.3m.

5. The safe distance will be defined between 240and 300m and according to the road and environmental conditions and various drivers' conditions this parameter will be an appropriate coefficient of the non-escaping point.

6. Based on the specific behaviors of Iranian drivers compared to the worldwide norm the desired  latency is set to be  be less than 600sec. Nevertheless, choosing the final latency will totally depend on the technical and economic factors.

Application objectives:

1. Sending "accident occurrence" warning message to the vehicles behind the crashed vehicle(s) up to distance of 600 m form the accident position.

System Requirements and Operations:

1. An Accident occurrence detection system is implemented in  OBUs (using the signals sent from the crash sensors that are used for enabling the air bag system or similar stuff, accelerators or the GPS data )

2. The crashed vehicle creates accident warning message  and broadcasts that every 0.5sec in order to warn other vehicle in the vicinity about the crash. (This packet contains the vehicle ID direction, location and the crash ID).

3.  A multi-hop safety message dissemination protocol is implemented for broadcasting accident warning messages to the approaching vehicles.  

4. The recipient vehicles validate the packet in terms of integrity and retrieve the position and direction of the crashed vehicle.

5. Having received this packet, other vehicles compare the location and direction information with their own position information and decide whether/not they are the target vehicles. (The vehicles on the same direction and behind the crashed vehicle are the target vehicles, so using this restriction mechanism the number of redundant messages will decease dramatically).

6. Displaying the "accident occurrence" warning message to the target vehicles will be either immediate warning or notification warning (for each incident the voice message will be played 2 times consecutively and the video message will be shown for three minutes- see the figure2).

figure2: A visual message is shown for the dirver along with a voice message 

7.  If there is any RSU in the propagation range of the warning message this message will be forwarded to the CCR.

Implementation Considerations:

1. The "accident occurrence' warning message will be sent to those vehicles that are at 300m away as an "Immediate Warning" and to the vehicles that are further away as a "Notification".

2. The packet broadcasting will be terminated by the police officers' command or after the relocation of the crashed vehicle to a safe location.

3. Since the GPS equipment is erroneous some of the vehicles that are in front of the incident location may receive the warning message as well.