**4.2.2 Optimal speed advice**

458 Wireless Communications and Networks – Recent Advances

As a conclusion, there is an apparent advantage in using wireless communication to broadcast information about the road conditions to the approaching drivers who will then have sufficient time to react. With this co-operative approach the RSU has the ability to transmit road condition information to the traffic management center which then can be analyzed and checked for accuracy and quality and transmitted to other vehicles that drive

The climate change that has been observed in recent years has also affected the priorities in the transport agenda. Nowadays minimization of CO2 emissions related to transport and environmental friendly driving comprises a top priority. The results of the CVIS project (CVIS, 2006-2010) have shown the added benefit from the use of wireless communication to enhance efficiency in transport. Examples of co-operative efficiency related applications will

In this application the infrastructure continuously collects information related to traffic density and makes forecasts for road segments with potential traffic jams. Then when an equipped vehicle drives next to a RSU the traffic density information on the neighboring area as well as driving instructions are transmitted to it. This information is processed by the vehicle and then the driver is informed about possible delays and alternative routes to avoid traffic jams. This way a significant number of drivers could be guided around congested areas so the entire transport system to become more efficient. A significant side effect of this application will be

Figure 7 shows an enhanced route planning scenario in which the RSU informs the driver of the red vehicle about heavy traffic ahead and suggests a faster alternative route to the driver's final destination. It is obvious from the description of this application that for its implementation a RSU with wireless communication is essential to provide the necessary information. A vehicle equipped only with some perception sensors, without communication capabilities, could make a rough estimation about the traffic density in the road segment it is currently driving, but without any information on alternative routes.

the reduction of pollution deriving from vehicles got stack in congested highways.

on this road segment.

be highlighted in the following.

**4.2.1 Enhanced route planning** 

Fig. 7. Enhanced route planning application.

**4.2 Efficiency** 

The aim of this application is to provide the needed information to the driver in an effort to make driving smoother and reduce significantly start and stop situations. As the vehicle approaches a signalized intersection it receives information about the exact position of the traffic light and the duration of its current status (e.g. the remaining seconds for the traffic light to become red).

Based on this information, that is using the distance from the intersection and the time until the traffic light turns to green, the approaching vehicle calculates the speed that it should follow to avoid stopping at the intersection. Then this "optimal" speed is provided to the driver and if this suggestion is followed it is very likely that the traffic light will turn into green as soon as the vehicle reaches the intersection and there is no need for it to stop. Fewer stops result in increased traffic flow and reduced fuel consumption for the equipped vehicles.

Figure 8 shows an example of this application in which the driver follows the optimal speed suggestion and thus will not have to stop at the intersection. For such kind of application to become a reality it is essential that the traffic light should be equipped with wireless communication capabilities.

Fig. 8. Optimal speed advice application.
