The Verge: Inside Waymo’s Strategy to Grow the Best Brains for Self-driving Cars

I’m really surprised if Waymo’s PerceptionRNN takes 4 months to train:

Neural nets need a surfeit of data to train. That means Waymo has amassed “hundreds of millions” of vehicle labels alone. … Operating every hour of every day of every week, and hitting 10 labels a second, it still takes Waymo’s machines four months to scroll through that entire dataset during its training process, Arnoud says.