There a three types of messages for this: First of all, there are periodic standardized messages that every car transmits to other cars and the RSUs up to ten times a second. They include the position, direction of motion and speed among other things. Secondly, there is event-based information such as notifications of accidents involving passenger cars or that the RSU recognizes because several vehicles are simultaneously braking fast. This also captures traffic jams because a lot of cars are standing still or slick roads when the ESP (electronic stability program) activates in other vehicles. Thirdly, there is application information. This is information on traffic-light sequences that vehicles can exchange with one another, along with traffic information generally. RSUs can also gather data from other sources such as radio and the traffic center. Other applications and the software for them are loaded wherever needed to launch the minimum configuration for the C2X system in order to go easy on the resources of the units. For more information please visit their site, follow the link.
update: The picture may have been altered in Photoshop.
Eavesdropper