Tech giant Google has been forced to add a steering wheel and pedals to its driverless car prototypes, due to new restrictions imposed by the California Department of Motor Vehicles (DMV).
The authority's rules state that driverless cars must be fitted with conventional controls, which would allow passengers to take over in the case of a software malfunction.
The requirement means that Google will have to retro-fit its fleet of development prototypes with a steering wheel and brake pedals if it wishes to continue testing on public roads.
Previously, the company had been using conventional vehicles fitted with its self-driving technology. These vehicles, being ready-fitted with human controls, are not affected by the new rules, though Google has already introduced a vehicle with no conventional controls whatsoever.
Rather than simply move its testing programme to another state, Google has decided to comply with the California-wide restriction by installing a "small, temporary steering wheel and pedal system", the Wall Street Journal reports.
"With these additions, our safety drivers can test the self-driving features, while having the ability to take control of the vehicle if necessary," Google spokeswoman Courtney Hohne told the newspaper.
100 of the bubble-shaped cars are now to be produced, as prototypes. All will be limited to 25mph and fitted with the temporary emergency controls. Tests involving members of the public, on open roads, are expected to commence within two years.
The introduction of steering wheels is not likely to be a permanent fixture, and is in place only as a prudent safety measure during initial testing, according to the Californian DMV.