It says the landing strip could also provide information about how long the vehicle should pause before driving off. "The wait period may enable a human who was driving the vehicle to exit the vehicle and remove his possessions," the filing says. "Additionally, the vehicle may be equipped with additional sensors that enable it to detect when the human has moved a sufficient distance away from the vehicle to allow safe autonomous operation." Google adds that the driver may not always wish to leave the vehicle after it has switched into automatic mode. It gives the example of a self-drive vehicle providing a tour of Chicago's Millennium Park with the machine programmed to stop at the site's ice rink, fountain and sculptures for set amounts of time before returning to its starting point.