It’s been the dream of science-fiction fans for more than half a century: You get in your car in the morning and say, “Take me to work,” and it automatically backs you out of the driveway and does exactly that — all on its own. When it gets to your office, it drops you off at the front door and then continues on its own into the parking garage.

More than just gee-whiz technology or a mere convenience, autonomy is seen as a means to minimize motor vehicle accidents, decrease traffic congestion and improve efficiency, which is why governments the world over are encouraging and enabling its development.

Right now, automakers truly are on the cusp of the kind of automation that signals that the future has arrived, one in which a car actually makes all of the decisions about travel, and it all works flawlessly. As we’ve explored in other articles, autonomous car hardware is here. It’s in vehicles you can buy and it’s just a of couple software patches away from being able to do much of what was just described.

But the question remains: When can I buy a truly autonomous car, one that only needs me to tell it where to go?

The Semi-Autonomous Near-Future (2016-2020)

As I write this, a 2017 Mercedes-Benz E-Class sedan has almost everything you’d need for a fully autonomous vehicle experience.

From the sensors to the telematics, all that the E-Class and its new Drive Pilot function would require is a software update to make it mostly (but not fully) autonomous. It’s so ready that Mercedes-Benz is testing autonomous versions of the E-Class on public roads. They’re using cars that are mechanically identical to ones you can buy in showrooms, just with different software.

Tesla and Volvo have fairly advanced semi-autonomous features, and more cars are expected to add these systems and services over the next four years, such that most luxury brands will offer them by 2020. They’ll show up at the high end of the price spectrum first, as the cost associated with this tech is easier to hide in a car that’s already expensive. But the technology to make the cars fully autonomous won’t be ready quite yet: The need to create the software needed for non-routine events on the road (construction, inclement weather, random incidents of unforeseen natures) makes that function a bit further out.

The Fully Autonomous Medium-Future (2020-2025)

The ability to summon a driverless car, one that may not even have controls for a human driver to operate, is coming after 2020, but before 2025, predicts researcher  IHS Automotive. The more interesting question: Which company will deliver it first?

Right now, all signs point to Google bringing fully autonomous technology to market. Not as an automobile manufacturer, but as a supplier of the electronic hardware and software needed to make all systems go. IHS points to Google’s massive ongoing investment and its ability to draw from adjacent technologies, including everything from robotics and artificial intelligence to detailed global maps, as giving it a significant edge over traditional automakers.

Perhaps the most interesting concept to come out of the autonomous car push is the idea of the “car as a service,” in which companies such as Uber, Lyft and others own the autonomous cars that you summon like a taxi. Uber in particular has invested heavily in autonomous-vehicle research, largely gutting Carnegie Mellon University’s program a couple of years ago by luring away dozens of top researchers and management. Automakers such as General Motors (with its newly announced Maven car-sharing service and its recent major investment in Lyft) and Ford (which has partnered with Google and created a Ford Mobility program) all are preparing for a day in which using an autonomous car does not necessarily mean owning that car.

By IHS’ estimates, that day is rapidly approaching. The company not only predicts that fully autonomous cars will be here before 2025, but projects that self-driving and driverless cars will account for 12 million vehicles sold globally just 10 years later in 2035. With nearly 85 percent of the world’s population without a driver’s license, that kind of technology could open up mobility in a dramatic way.