If it helps this will be hard in any other software as well, unless they handle it specifically.
Anyways no pathfinding needs to be done at all, unless you need the cars to have a specific destination, otherwise they can just meander.
Here's one idea:
https://www.dropbox.com/s/dl5b7om2qwweo ... .capx?dl=1
Basically it's a bunch of waypoints connected to make paths. The waypoints can have multiple outgoing paths, so the cars just pick a random one. I made an in game editor so creating the connections is easier. I then can copy the result to a variable and remove the editor if i want to.
Next step is to make the cars move. I suppose the moveto behavior could have been useful, but I opted to just use events to move from one waypoint to the other. Pretty much the only requirement I had was to specify when to move.
The car to car awareness proved slightly complicated. It was simple enough to make the car's angle face the direction it was going. Then i could see if another car was ahead with the overlapping at offset condition. That isn't enough for intersections, which would bind up with just that rule. My solution was to only let one car travel through the intersection at one time. It's random so maybe actually making traffic laws would help.
Overall it works pretty well, however the logic for intersections fails in a few places near intersections, so that would need more work.
There may be other simpler ways. Standby for a sightly different idea.