Google’s Driverless Cars Run Into Problem: Cars With Drivers

Google, a leader in efforts to create driverless cars, has run into an odd safety conundrum: Its cars don’t make enough mistakes.

Last month, as one of Google’s self-driving cars approached a crosswalk, it did what it was supposed to do when it slowed to allow a pedestrian to cross, prompting its “safety driver” to apply the brakes. The pedestrian was fine, but not so much Google’s car, which was hit from behind by a human-driven sedan.

Google’s fleet of autonomous test cars is programmed to follow the letter of...