A driverless Waymo in downtown Austin, Texas. Bob Daemmrich/ZUMA Press This was supposed to be the year that robotaxis hit Main Street across the U.S., as companies like Alphabet’s GOOGL -2.51%decrease; red down pointing triangle Waymo, Tesla and Amazon.com’s Zoox launch AI-powered autonomous rides in dozens of cities. But as hundreds of robot cars collide with humans, both literally and figuratively, tensions are rising.