US vehicle safety regulators have told Google that an artificial intelligence system can be considered a driver under federal law, opening the door to autonomous vehicles that do not need qualified drivers in them to operate.
In a letter to the search giant, The National Highway Traffic Safety (NHTSA) said: "NHTSA will interpret 'driver' in the context of Google's described motor vehicle design as referring to the [self-driving system] and not to any of the vehicle occupants."
The new ruling enables Google to progress with its plans to develop a car with "no need for a human driver", a proposed design which was submitted in November last year.
"We agree with Google its [self-driving car] will not have a 'driver' in the traditional sense that vehicles have had drivers during the last more than one hundred years," the letter continued.
A number of major automakers are currently developing the technology, with some already selling vehicles that can drive themselves in certain conditions, such as on the highway.
The Renault-Nissan Alliance recently announced that it planned to release 10 vehicles with autonomous drive technology in the next four years, with the first models arriving as early as 2016.
Ford has also entered the fray and it has been reported that they are considering teaming up with Google to produce some of its first commercial vehicles.
Many of the protagonists working on autonomous driving have complained that US state and federal safety rules are impeding the testing and eventual deployment of such vehicles.
California has proposed draft rules that require steering wheels and a licensed driver in all self-driving cars, which Google feels is restrictive and would slow deployment of the technology on American roads.
Karl Brauer, a senior analyst for the Kelley Blue Book automotive research firm, said there were still significant legal questions surrounding autonomous vehicles.
He admitted that if the NHTSA is prepared to name artificial intelligence as a viable alternative to human-controlled vehicles, "it could substantially streamline the process of putting autonomous vehicles on the road".
If the car's computer is the driver for legal purposes, then it clears the way for Google or automakers to design vehicle systems that communicate directly with the vehicle's artificial pilot.
In its letter to Google, the NHTSA, said that a number of issues still needed to be overcome and that further discussion would need to be had: "The next question is whether and how Google could certify that the [self-driving system] meets a standard developed and designed to apply to a vehicle with a human driver."
Google is "still evaluating" NHTSA's lengthy response, a company spokesperson said.
It believes its autonomous vehicles will have a number of advantages over traditional cars outside of the obvious benefits. AI drivers have the potential to be safer, as human error is considered to be responsible for the large majority of road accidents.
Google’s technology could also bring energy efficiency savings, with cars automatically taking the route with the lowest fuel use and regulating their speed to get the best mile per gallon.
However, a recent study has shown that around a fifth of the energy-saving benefits of fuel-efficient cars are eroded because people end up driving them more.
Research by the University of Sussex that looked into British motoring habits over the last 40 years found that lower cost driving resulted in a "rebound effect" that lead to car owners using their vehicles 20 per cent more.
The team looked at both improvements in fuel efficiency and reductions in fuel prices to determine their impacts on the habits of drivers.
In an attempt to make their estimate as accurate as possible, the Sussex researchers tested more than a hundred different models, each focusing on different variables.
Dr Lee Stapleton, with the University's Centre on Innovation and Energy Demand, said, "Improvements in fuel efficiency should lead to reductions in fuel consumption, but since improved fuel efficiency makes driving cheaper, some of the potential fuel savings are 'taken back' through increased driving.
"We call this the rebound effect and it is well-documented in other sectors. For instance, we know that insulation of housing encourages people to enjoy warmer homes, rather than taking all the benefits in the form of lower bills.
"Until now, we didn't know the size of this effect for British motoring. We found evidence of a significant, long-term rebound and expect our results to be of interest for public policy."