AnyLogic provides traditional traffic lights which are triggered on the basis of time. I am creating a new road traffic management system in which I want to trigger traffic lights on the basis of the greatest car density among the four roads. Is there any function or element that would help me to do so?
No, you need to code it yourself.
That, however, is entirely possible. Just learn more about AnyLogic and how to write code, how to count cars on a road, how to manually switch traffic lights, etc.
Then, you can easily make it happen.