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It's beginning to seem like a foregone conclusion: 25 years from now the roads will be filled with millions of self-driving cars, as automakers and legislators aim to cut back on congestion and accidents.

Gary Silberg, who forecasts future trends in the auto industry for consulting firm KPMG, estimates close to half of all new vehicles sold in 2039 will offer the option of fully autonomous driving. Navigant Research forecasts 94.7 million vehicles with self-driving capabilities will be sold annually around the world by 2035.

Bob Lutz, former vice chairman at General Motors, said that most vehicles will be autonomous, taking the concept one step further.

According to Lutz, in 25 years most vehicles will be nondescript people carriers that chauffeur passengers on high-speed freeways, where inductive electric lines in the pavement recharge the module as they zip along. (See an animation of his vision below.)

Although he admits the vision requires federal and state lawmakers to invest billions of dollars to build an electrified highway, he said he doesn't see another solution to today's transportation bottleneck.

"People are spending hours that could be productive for society; they are spending it bogged down in traffic," Lutz said.

The race is on

At the Mercedes-Benz Research & Development North America center in Sunnyvale, California, Johann Jungwirth, president of the division, agreed that autonomous cars are coming in the not too distant future. In fact, much of the technology is already being tested.

Several automakers, including Mercedes-Benz, Audi, General Motors and Nissan, have shown prototypes of self-driving cars. Nissan CEO Carlos Ghosn said his company will have an autonomous car on the road by the end of the decade.

Google, which many credit with sparking America's fascination of driverless cars, recently showed a second-generation car with no steering wheel, just a panic button for emergency stops.

"The technology has evolved. The sensors, actuators and so on are already there. It is really about integration. We are along the path to get there and I foresee that day coming," Jungwirth said.

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It's not just tech firms and automakers racing toward a world of self-driving cars. In Ann Arbor, the University of Michigan's Mobility Transportation Center has been studying how cars and drivers interact to create a "driverless city." The goal: making it safer for millions of people to get from point A to point B.

According to the Insurance Institute for Highway Safety, there were approximately 5.6 million vehicle crashes in the U.S. in 2012, the most recent year with available data. That year, 33,561 people were killed in traffic accidents, according to the National Highway Transportation Safety Administration.

Jungwith said many accidents could be prevented if software controlled the vehicle's speed and steering.

"We are taking the driver somewhat out of the loop," he said.

The messy transition to autonomous

Don Norman, director of the Design Lab at the University of California, San Diego, said autonomous drive vehicles are a wonderful idea, but the transition from driver-operated to driverless is likely to be filled with accidents.

"When you have two types of vehicles on the road, it will be very messy," he said. "For example, what if two vehicles [are] approaching an intersection and the cars talk to each other as the stoplight goes from green to yellow. One car may calculate it should speed up to clear the intersection, but if the driver in that car thinks that's the wrong move and hits the brake, there will be an accident."

Overall, Norman said he thinks the number of accidents and fatalities from crashes will drop considerably when fully autonomous drive vehicles are the dominant vehicle on the road. However, when there are accidents with driverless cars, he predicts they will likely be worse.

"If autonomous drive vehicles are going faster speeds and are spaced closer together, when something goes wrong the accidents will be more severe," he said.

Critics also cite the need for lawmakers to address the rules of self-driving vehicles before they can take off.

Cutting back on congestion

Think it's crowded on the roads right now?

In 25 years the U.S. Census Bureau predicts America will be home to about 400 million people — meaning more congestion on the nation's highways. Navigant Research estimates another 10 million vehicles will be in use by 2035, bringing the total number on American roads to more than a quarter billion.

"We will definitely see more traffic jams in 2039, longer rush hours probably as well," said Marc Winterhoff, a partner with the consulting firm Roland Berger.

Although subways and public buses will continue to see healthy use, self-driving cars are seen by many as the biggest hope for easing congestion in urban areas. Through real-time traffic data that will constantly calculate if there's a route with less traffic, they will cut back on human error that creates traffic jams.

Their promise to eliminate the need to drive around for parking, which Roland Berger estimates causes 30 percent of congestion in urban areas, could also significantly cut down on traffic. After dropping passengers off, the autonomous car would go straight to a parking space or garage where it already knows a spot is waiting.

"We will definitely see more traffic jams in 2039, longer rush hours probably as well."

Winterhoff said autonomous trucks will also impact how businesses and shipping companies send their goods, and free up roadways as a result. By using software developed for shipping and logistics operations, these trucks could operate at off-peak or overnight hours. Both Daimler and Volvo are already developing trucks where the driver is not in control.

Car sharing is also expected to become more popular in the future. Navigant estimates the number of people who belong to these programs will skyrocket from 1.5 million today to 11 million by 2024, and far higher by 2039.

Experts also predict that 25 years from now, the 9-to-5 workday will be a thing of the past for many. This will make rush hours longer, but with fewer times of peak traffic.

"People are adapting," Gartner said.