In simulation games like Sim City and Factorio, there are numerous interaction between tiny objects that needs to be animated. e.g. random people walking on the sidewalk, then waits for a bus, then board the bus; tiny cars waiting in line for each other at the traffic junction; thousands of items on a convey belt and the robotic arm needs to wait for and item to arrive in front of it to pick it up; conveyor belt sections transferring items from one to another;

I think we cannot check collision detection for every tiny object independently as it will eat a lot of CPU, then what is the technique we can use in these games?

In simulation games like Sim City and Factorio, there are numerous interaction between tiny objects that needs to be animated. e.g. random people walking on the sidewalk, then waits for a bus, then board the bus; tiny cars waiting in line for each other at the traffic junction; thousands of items on a convey belt and the robotic arm needs to wait for an item to arrive in front of it to pick it up; conveyor belt sections transferring items from one to another.

I expect the collision detection check for every tiny object independently will eat a lot of CPU; what technique can I use in such a game to avoid the heavy computation and make it look like it's realistic?