Volkswagen will unveil a concept for a large, electric sedan with fully self-driving capability at next week's 2018 Geneva International Motor Show. The concept doesn't preview a specific model currently in the pipeline, though elements from its design may influence a new Phaeton due around 2020.

What the ID Vizzion represents is VW's vision for self-driving cars of the future and the opportunities the technology presents, such as new types of control interfaces and augmented reality interaction.

But there's a long road ahead to reaching that reality. Because of the massive societal change required, as well as the need for a build-up in infrastructure, the transition to self-driving cars will be a gradual process.

In 2014, the Society of Automotive Engineers adopted a common taxonomy for self-driving cars that clearly defined six levels—from Level 0 to Level 5—of automation. The boundaries are pretty obvious. Level 0 is no assistance and Level 5 is full automation. The Vizzion concept is at Level 5.

Teaser for Volkswagen ID Vizzion concept debuting at 2018 Geneva auto show

The highest level yet to be achieved in a production car is Level 3, referred as Conditional Automation. This means a car can drive itself in specific conditions but requires a human to be alert and ready to take over outside of those conditions. Companies, however, are finding that it's difficult for humans to maintain alertness so many are deciding to skip Level 3 and go straight to Level 4.

Level 4, High-Level Automation, is similar to Level 3 but has the added advantage that it can bring a car to a safe stop on its own should a human fail to take over when required. Level 4 self-driving cars are almost upon us. Waymo will start a commercial ride-sharing service in Phoenix, Arizona later this year using a fleet of Level 4 self-driving cars. General Motors is aiming to start a similar service in 2019. VW aims to have its own Level 4 self-driving cars operating by 2021.

As for Level 5, Full Automation, it might not happen for decades as it will require cars that can drive themselves in all conditions, all of the time. Considering most of the nation's roadways aren't pencil-straight interstates on a sunny day, the final level will require extensive testing for sensors or AI systems that can handle road lines in bad weather, low light, dirt roads, or countless other variable circumstances. There would also need to be substantial infrastructure set up, especially in regards to map data and communication between vehicles and their surrounding environments.