How Self-parking Cars Work

The British Toyota Prius with Intelligent Parking Assist has a dashboard screen to tell the driver what to do. See more car safety pictures.
Image courtesy Toyota Motor Europe S.A./N.V.


Parallel parking is an ordeal for many drivers, but with parking space limited in big cities, squeezing your car into a tiny space is a vital skill. It's seldom an easy task, and it can lead to traffic tie-ups, frazzled nerves and bent fenders. Fortunately, technology has an answer - cars that park themselves. Imagine finding the perfect parking spot, but instead of struggling to maneuver your car back and forth, you simply press a button, sit back, and relax. The same technology used in self-parking cars can be used for collision avoidance systems and ultimately, self-driving cars.


Automakers are starting to market self-parking cars because they sense a consumer demand. Parallel parking is often the most feared part of the driver's test, and it's something almost everyone has to do at some point. People who live in big cities may have to do it every day. Removing the difficulty, stress and uncertainty of this chore is very appealing.

Self-parking cars can also help to solve some of the parking and traffic problems in dense urban areas. Sometimes parking a car in a space is restricted by the driver's skill at parallel parking. A self-parking car can fit into smaller spaces than most drivers can manage on their own. This makes it easier for people to find parking spaces, and allows the same number of cars to take up fewer spaces. When someone parallel parks, they often block a lane of traffic for at least a few seconds. If they have problems getting into the spot, this can last for several minutes and seriously disrupt traffic.

Finally, the difficulty of parallel parking leads to a lot of minor dents and scratches. Self-parking technology would prevent many of these mishaps. It can also save money, since you won't have to worry about insurance claims for parking-related damage.


Self-parking Technology

Self-parking technology is mostly used in parallel parking situations (although BMW has a prototype that parks itself in horizontal spaces, like small garages). Parallel parking requires cars to park parallel to a curb, in line with the other parked cars. Most people need about six feet more space than the total length of their car to successfully parallel park, although some expert drivers can do it with less space.

To parallel park, the driver must follow these five basic steps:


  1. He pulls ahead of the space and stops beside the car in front of it.
  2. Turning the car's wheels towards the curb, he backs into the space at around a 45-degree angle.
  3. When his front wheels are even with the rear wheels of the car in front of him, he straightens them and continues backing up.
  4. While checking his rear view to be sure that he doesn't come too close to the car behind him, the driver turns his wheels away from the curb to swing the front end of his car into the space.
  5. Finally, the driver pulls forward and backwards in the space until his car is about one foot away from the curb.

Self-parking cars currently on the market are not completely autonomous, but they do make parallel parking much easier. The driver still regulates the speed of the vehicle by pressing and releasing the brake pedal (the car's idle speed is enough to move it into the parking space without pressing the gas pedal). Once the process begins, the on-board computer system take over the steering wheel.

The car moves forward into position beside the front car, and a signal lets the driver know when he should stop. Then the driver shifts the car into reverse and releases the brake slightly to begin moving backward. Using the power steering system, the computer turns the wheel and perfectly maneuvers the car into the parking space. When the car has backed far enough into the space, another signal lets the driver know that he should stop and shift the car into drive. The car pulls forward as the wheels adjust to maneuver it into the space. A final signal (on the British Toyota Prius, it's a female voice that intones, "The assist is finished.") tells the driver when parking is complete.

On the British Toyota Prius, a large computer screen mounted on the dashboard gives the driver notifications such as when to stop, when to shift into reverse, and when to slowly ease off the brake to move the car into the parking spot.

Different self-parking systems have different ways of sensing the objects around the car. Some have sensors distributed around the front and rear bumpers of the car, which act as both transmitters and receivers. These sensors transmit signals, which bounce off objects around the car and reflect back to them. The car's computer then uses the amount of time that it takes those signals to return to calculate the location of the objects. Others systems have cameras mounted onto the bumpers or use radar to detect objects. The end result is the same: the car detects the other parked cars, the size of the parking space and the distance to the curb, then steers it into the space.

Next, we'll look at the specific models on the market and what's in store for the future.



Future Self-parking Cars

2006 Toyota Prius
Image courtesy Toyota Motor Europe S.A./N.V.

­­In 1992, Volkswagen employed self-parking technology in its IRVW (Integrated Research Volkswagen) Futura concept car. The IRVW parked with full autonomy - the driver could get out of the car and watch as it parked itself. A PC-sized computer in the trunk controlled the system. Volkswagen estimated that this feature would've added about $3,000 to the price of a car, and it was never offered on a production model [ref].

In 2003, Toyota began offering a self-parking option, called Intelligent Parking Assist, on its Japanese Prius hybrid. Three years later, British drivers had the option of adding self-parking to the Prius for the equivalent of $700. So far, seventy percent of British Prius buyers have chosen this feature [ref]. Toyota plans to introduce the self-parking Prius to the United States in the near future, but no date has been set.


Although Toyota is currently the only company with a self-parking car on the market, others have self-parking systems in the works. In 2004, a group of students at Linköping University in Sweden collaborated with Volvo on a project called Evolve. The Evolve car can parallel park autonomously. The students fitted a Volvo S60 with sensors and a computer in its trunk, which controls the steering wheel as well as the gas and brake pedals. You can see a video of this car in action here. Seimens VDO is working on a standalone driver assistance system called Park Mate, which would help drivers find a space as well as park in it.

Seimens VDO's Park Mate would help drivers find parking spots as well as park in them.
Image courtesy Seimens VDO

A car that can take control of the wheel to park itself is one thing, but a self-driving car is another. It seems like a futurist's dream: millions of fuel-efficient cars driving smoothly under computer control, safely avoiding collisions and maintaining safe speeds, while the "drivers" sit back and watch TV or take a nap. How far are we from a "Jetsons"-like autotopia? Probably pretty far.

Many people enjoy driving, so it might be difficult for them to relinquish control of their vehicles to a computer, even if it would be safer. Product liability laws also have to be taken into account. However, the technology isn't far away. General Motors plans to offer a self-driving 2008 Opel Vectra to German drivers. The car will drive by itself at 60 mph, using a system of cameras, lasers and computers to track lanes, road signs, curves, obstacles and other cars. [ref].

The 2008 Opel Vectra at the 2006 Opel Zentrum in Berlin, Germany.
Public domain image

Some cars already have a semi-automated cruise control system, known as adaptive cruise control. This system allows the driver to set a speed, just like regular cruise control. However, this system uses lasers to detect the distance to any vehicles on the road ahead, and automatically slows the car down if it gets too close.

Another upcoming development would use wireless technology to connect cars to each other. If one car detected slippery conditions on a curve, cars behind it would receive the information and slow down. Traction control systems would also kick into action. In addition, this system could detect traffic conditions by tracking the speeds of other cars and then suggest alternate routes.

While self-parking cars might seem like a frivolous luxury at the moment, they're actually the next step in the evolution of automotive technology.For lots more information about self-parking cars, car systems and related topics, check out the links on the next page.


Lots More Information

Related HowStuffWorks Articles

More Great Links

  • "A Car That (Really) Drives Itself: The 2008 Opel Vectra." Edmunds.
  • Ditlea, Steve. "Self-parking cars." Omni, Sept. 1992. mi_m1430/is_n12_v14/ai_12516738
  • Horrell, Paul. "The Future of the Car." Popular Science. f2909aa138b84010vgnvcm1000004eecbccdrcrd.html
  • "Self-parking cars coming into U.S."
  • "Volvo car's self-parking system."