This was fixable with a very basic mod. There was a heuristic value which basically determined how far out of the way the traffic simulator would look when try

This was fixable with a very basic mod. There was a heuristic value which basically determined how far out of the way the traffic simulator would look when trying to find a path. But it was a trade-off for simulation speed. The mod changed this value and allowed the sim to try more paths, but made time move MUCH slower, even with the game speed set to max, once your city started getting large. It was worth it though to see your highways and public transit actually get used.