This wall remains a silly and contrived test. Rober did it for the fun of recreating the Road Runner cartoon scene, not because it’s an important thing for self-driving cars to detect.

When 2-year-old Liam saw his grandma arrive at Peoria International Airport in Illinois, he reacted like a cartoon road runner. Liam and his grandma, Julie Bielfeldt, or "Gam Gam" as he calls her ...