The biggest flaw in C:S traffic flow, even with the popular traffic improvement mods, is that routes and lane choices are pre-calculated when the vehicle departs and don't really take into account alternative routes/lanes or current traffic load very well or at all. You quickly run into issues where you'll have a 3 lane road that has 99% of the cars backed up in one lane while the other 2 are wide open. Coincidentally it kind of mimics an induced demand problem, but for the wrong reasons.

Of course having every vehicle continually recalculate and optimize its path is computationally prohibitive. Given the limitations it does a pretty good job, though!