That’s the question. Let’s say the roads are now exclusively self driving cars and they are so efficient they double the throughput of roads. Meanwhile commuters bought houses that are twice as far away from the city because those houses are cheaper, and now they can sleep and work in the car anyway, so twice as much traffic. Or all schoolkids not taking the schoolbus anymore and all going by individual autonomous car and all pensioners getting their robo-taxi to squeeze through rush hour every morning so they’re first at the supermarket for the freshest produce. It remains to be seen how that works out.