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.

Image courtesy Stock.xchng In many places, the only parking option is parallel parking.

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.

Go Park Yourself
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.

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

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.