Despite test-drive encounters with deer and a woman in an electric wheelchair chasing a duck down the middle of the road, Google is pushing ahead with plans to introduce its prototype driverless cars to Austin, Texas, this month.
The search-to-advertising giant has been conducting two months of road trials in the Texan state capital, to study how communities perceive and interact with the Lexus RX450h SUVs and to refine how the vehicles behave, so that they feel as natural as possible to passengers and those around them.
Google's Self-Driving Car Project has 23 of the Lexus cars and 25 prototype vehicles, five of which are already self-driving on public streets in Mountain View, California.
"We're just starting to test our prototype vehicles; we have a few on the streets of Mountain View now, and they'll be arriving in Austin in early September," Google said in its monthly project report.
Since the start of the initiative in 2009, its cars have clocked up 1,158,818 miles in autonomous mode, where software is doing the driving, and are currently averaging about 10,000 miles per week in public.
The self-drive technology is designed to cope with the unpredictable actions of humans and wildlife. Sensors on the vehicles can detect animals even at night and on the side of the road.
"Apparently Austin has a lot of deer, and we're ready for them. Rather than teaching the car to handle very specific things, we give the car fundamental capabilities for detecting unfamiliar objects or other road users, and then we give it lots of practice in a wide range of situations," Google said.
"Most often the best approach - for our software or for a human driver - is to slow down or come to a stop until more information about the situation is available. And because the car has 360-degree visibility out nearly 200 yards in all directions at all times and is always paying attention, it should be able to detect and respond to tricky situations before they get really sticky."
As well as substantial mileage on public roads, Google also has a team working on problematic scenarios on the project's test track.
"Sometimes they're difficult variations on what we've seen out on the roads - a car suddenly pulling out from a parking spot right into our path - and sometimes they're diabolical creations of the team's imagination. We've done everything from throwing piles of loose paper in the road to purchasing giant stuffed birds from a Halloween store."
Despite those efforts, in the six years of the project, Google's driverless cars been involved in 16 minor accidents, in more than two million miles of autonomous and manual driving.
"Not once was the self-driving car the cause of the accident," the company said.