As an aside: Why are robocars practicing on wide, sunny roads in the American southwest? Shouldn’t they test on the hard cases? Rain, Snow, alleyways, streets,

As an aside: Why are robocars practicing on wide, sunny roads in the American southwest? Shouldn’t they test on the hard cases? Rain, Snow, alleyways, streets, that exist since medieval or earlier times, traffic which takes a laissez-faire approach to rules?