“How does the driver know what is their responsibility and what is the vehicle’s responsibility?” said Jim Sayer, director of the University of Michigan Transportation Research Institute. If a car’s computer system can’t detect that there’s a problem ahead on the road, it wouldn’t even know to alert the driver, he said. Carmakers are trying to understand how humans behave when they’re retaking control of a vehicle that has been driving in autonomous mode. Audi is researching that topic in cooperation with the Virginia Tech Transportation Institute. One aim of the study is to figure out what people do when they’re not driving and how fast they can take over, said Brad Stertz, spokesman for Audi of America.