veins - how to send a message to change speed when an accident occurs.

[Oshadhi Gunathileke]

Hi! I'm a beginner to omnet++ and veins. 

I want to implement a scenario where the nearby vehicles change thier speeds when an accident occurs infront of them. The speeds should be allocated to each vehicle depending on their distance to the accident location. I don't know how to make this happen. 

Please help me.