[tempaccount9473]

The best example of a working and fun open-source routing/pathfinding engine is http://www.openttd.org

It's optimized for gameplay rather than perfect efficiency, but parts of it are quite hackable, including the ability to add custom AIs

[EvanKelly]

I just started playing openttd, and am having a great time, though I still struggle with complex rail networks.

Do you have recommendations for AI? I've been using NoCAB, but I'm kind of frustrated with how that AI works, so I almost always play solo games now.

[duck]

Thanks for sharing that, I had no idea that existed and I loved TTD!