I used METR-LA — 207 loop sensors across Los Angeles highways — and built an A3T-GCN, a graph neural network that reads space and time at once. A graph convolution lets every sensor borrow its road-neighbours' readings, a GRU reads the last hour, and an attention layer decides which moments matter. It forecasts speed 60 minutes ahead. The point of the graph is simple: a jam upstream reaches you a few minutes later, and a plain per-sensor model can't see that coming.
The model on its own isn't the interesting part. I fed its forecasts into a SUMO simulation and let them drive the traffic lights on a 3×3 grid through TraCI. Against fixed-time signals, the adaptive version cut average waiting time by 79%.



