In Cities Skylines every car takes the theoretically fastest route to get to their destination. This is somewhat realistic as this is how most people IRL determ

In Cities Skylines every car takes the theoretically fastest route to get to their destination. This is somewhat realistic as this is how most people IRL determine which way to drive as well, however the cars will follow this even when it is clear that the route they will take will have a major backup or congestion and another route is only marginally slower and will be completely empty. Additionally, and perhaps more importantly, drivers don't reroute when a direction slows. They will stick with the route they are going until they get to their destination.