It seems as though Google's driverless car won't be on the road as soon as previously expected.

While Google and other auto companies have been working hard to create a car that is truly driverless, in truth it could be decades before this dream becomes a reality.

A report released last week by the MIT Technology Review says that because driverless cars rely so heavily on maps and other detailed data, they will not be able to drive themselves around 99 percent of the U.S.

Not only that, but driverless cars also won't be able to make their way around roads in heavy rain or in snow or be able to react like a human, dodging things like potholes and other obstacles.

The reason for this is that the detection technology is not yet at a point where it can discriminate between weather conditions and other obstacles. While the car can determine what color is lit up on a traffic light, sunlight could confuse it.

Chris Urmson, director of the Google Car team, admits that there are a lot of obstacles to overcome with the project.

"I could construct a construction zone that could befuddle the car," Urmson said.

Not only that, but the car also detects pedestrians as a moving column of pixels. Because of this, the car would not be able to tell the difference between a normal pedestrian and a police officer waving at traffic to tell it to stop.

The journey itself is not the only area for concern with Google's driverless cars. Before any journey is made, an extremely detailed route needs to be made. The process of creating this route is far more complex than anything Google has done to date with Google Maps. Google would need to pour resources into making a far more detailed version of Google Maps, down to the last tiny detail. Each driveway would need to be precisely noted, as well as each sign and so on.

Despite the setbacks, according to Urmson the car will be on the road sooner than people may think, perhaps even within the next five years. A personal goal for Urmson is to have driverless cars ready for the road by the time his 11-year old son turns 16.

While Google has unveiled a driverless car prototype without a steering wheel, the company will have to add a steering wheel to the design to comply with regulations set by the California Department of Motor Vehicles.