Traditionally, Google's self-driving car prototypes have taken existing cars from manufacturers like Toyota and Lexus and bolted on the self-driving car components. This is less than ideal, since it limits the design possibilities of the car's "vision" system and includes (eventually) unnecessary components, like a steering wheel and pedals.

However, Google recently built a self-driving car of its own design, which had no human control system other than a "go" button. The California DMV has now thrown a speed bump in Google's car design, though, in the form of new testing regulations that require in-development self-driving cars to allow a driver to take “immediate physical control” if needed.

The new law means Google's self-designed car will need to have a steering wheel and gas and brake pedals while it is still under development. According to The Wall Street Journal, Google will comply with the law by building a "small, temporary steering wheel and pedal system that drivers can use during testing" into the prototype cars. The report says California officials are working on rules for cars without a steering wheel and pedals, but for now, a human control system is mandatory.

Self-driving cars have the potential to change the way automobiles are made, and Google's prototype car was just the first step toward that future. Cars today are built to crash, with tons of metal reinforcement, crumple zones, seat belts, and a million air bags. When everything is self-driving, and cars never (or at least rarely) crash, most of that safety equipment can be ripped out, resulting in a much lighter, more fuel-efficient vehicle. You also don't really need headlights, windows, or mirrors, since all of those are human vision assistants. All of these things make sense in a fully autonomous future, but lawmakers will have a tricky time deciding when that changeover can happen.

Google has taken a few steps toward that future with its self-designed electric vehicle, and while adding a steering wheel and pedals will dial the futurism back a notch, the cars are still beneficial in other ways. Google made the front and back of the car nearly flat, giving the roof-mounted LIDAR and other sensors a less-obstructed view of things around the car. The ground-up design also allowed Google to embed sensors in an optimal position without worrying about mounting them to an existing structure. The cars are even fully electric, allowing Google to test its cars while causing a minimal carbon footprint.

Another interesting tidbit in the WSJ mentions Google's desire to explore self-driving vehicles in other form factors. Google petitioned the DMV to allow it to test automated trucks and motorcycles on the public roads, but the DMV declined.

The report says Google hopes to put regular drivers in autonomous cars in "a couple of years," and the company is thinking that the cars would be valuable when provided as a service—like an automated taxi. Claire Hughes Johnson, a Google self-driving car executive, was quoted as saying "You may not be able to buy one, but you may be able to drive in one in the next five years."

Update: We've updated this post to clarify that the steering wheel and pedals are only required for self-driving cars that are still in development. The California DMV rules will allow for consumer versions of autonomous cars without direct controls.