Because there is no "100 percent watertight definition" of autonomous cars today, as Riches pointed out, perhaps it's useful to describe different levels, according to five definitions put together by the US Department of Transportation's National Highway Traffic Safety Administration earlier this year.
Level 0, according to the NHTSA, is a car with no automation. The driver is (we hope) in complete and sole control of the primary vehicle controls, such as brake, steering, throttle, and motive power, all the time.
Level 1 indicates a car with one or more function-specific automation control functions -- including electronic stability control or pre-charged brakes. In other words, this allows the vehicle to automatically assist with braking to enable the driver to regain control of the vehicle or stop faster than possible by acting alone.
Level 2, meanwhile, offers combined-function automation, offering at least two primary control functions designed to work in unison to relieve the driver. An example would be adaptive cruise control in combination with lane centering.
Level 3 provides limited self-driving automation, enabling the driver to cede full control of all safety-critical functions under certain traffic or environmental conditions. The driver is expected to be available for occasional control, but with sufficiently comfortable transition time. The NHTSA sees the Google car as "an example of limited self-driving automation."
Level 4 is defined by the NHTSA as "full self-driving automation." The vehicle is designed to perform all safety-critical driving functions and monitor roadway conditions for an entire trip. Such a design anticipates that the driver will provide destination or navigation input, but is not expected to be available for control at any time.
Strategy Analytics' Riches noted, "I would start calling a vehicle 'semi-autonomous' at NHTSA's Level 2, progressing into level 3." Meanwhile, the term "fully autonomous" is reserved for Level 4 automation, he added. "Essentially, if the driver needs to be present and ready to take control if required, then the vehicle is only semi-autonomous."
For any market research firm, predicting the future 20 years ahead is tricky business and inexact science. Riches described any forecast that extends to 2025 and beyond as "more in the realm of future-gazing than modeling."
Navigant Research's Alexander, while acknowledging the challenge, noted, "Twenty years is a long way out, but we're making predictions based on the technologies that are already available," and information the firm has gathered on rollout plans by the industry.
When asked about the huge jump in self-driving cars from 8,000 annually in 2020 to 95.4 million in 2035, Alexander said, "We see it no different from how cars with adaptive cruise control rapidly grew within a short of five years, from the early 2000s when the market was very small."
Strategy Analytics, in contrast, takes a more conservative view. Riches explained: "Looking at the latest forecast data, the percentage of light vehicles worldwide fitted with all of autonomous cruise control, lane departure warning, and blind spot monitoring was less than 1 percent in 2010 and is projected at around 5 percent in 2015, rising to 9 percent in 2020."
Riches further projected the percentage of vehicles with all three of these technologies (and thus the prospect of being partially/fully autonomous) at around 13 percent in 2025 and 18 percent in 2030. However, he acknowledged that these numbers could be "an underestimate, as we would expect growth to pick up as technologies get cheaper and more legislation is enacted mandating a certain level of driver support."
The elephant in the room
Both Navigant Research and Strategy Analytics agreed that the elephant in the room, in any discussion of self-driving cars, is the absence of a legal framework for autonomous cars.
As Alexander described, the main barrier under the Geneva Convention on driving law, for all vehicles, is that drivers must be in charge of driving and be in control at all times. He explained, "Some US states and European countries have begun to issue licenses to companies to conduct testing of autonomous driving features on public highways under controlled conditions."
But that permit requires new legislation. Complicating the matter further, automotive OEMs do not wish to be held liable for any accidents caused by self-driving cars.
Riches noted: "Ultimately, it will be the vehicle manufacturer who has to stand behind their product. But they will probably need clarifications and likely [make] changes to current product liability laws before they can advertise and sell fully autonomous vehicles."