I remember from my time at Udacity that easy-to-use open-source simulators are hard to come by. Waymo just released Waymax, a simulator for behavioral planning, which looks pretty cool.
The simulator is written with JAX, an ML-focused numerical analysis library, which sets up Waymax to work nicely with neural networks.
The GitHub repo has some pretty nice Google Colab tutorials, which I might try out over the coming days.
David Silver 