DEARBORN, Mich. — His family made its fortune selling cars to the masses, but now Bill Ford Jr. is fretting about selling too many.

The great-grandson of Ford Motor Co. founder Henry Ford has been thinking ahead to a time when there will be too much traffic in the world’s major cities. Already there is congestion that only will get worse as the world population grows by another 2 billion people to 9 billion in 40 years.

Now he’s sounding the alarm in public. Today he’ll tell a mobile electronic device conference in Barcelona, Spain, that the industry should join with automakers and governments to develop technology that would solve the looming congestion problem. He doesn’t know the ultimate solution, but he sees a day when cars communicate with each other and with roads, traffic lights and public transportation to move people and traffic safely.

Ford, executive chairman of the Dearborn, Mich., automaker, is concerned that congestion could get so bad that people won’t get goods and services such as health care.

“What I’m really worried about is the role of the car in the long-term,” he said in a recent interview with The Associated Press. “If we do nothing, it will limit the number of vehicles we can sell. If we can solve this problem of urban mobility, I think there’s a great business opportunity for us.”

Ford, 54, who in the past has tried to deal with the environmental impact of cars and trucks, is now focused on urban congestion. He’s free to think about the future since he no longer has to worry about Ford’s day-to-day operations. The company is making billions under CEO Alan Mulally.

Ford is not so concerned about auto pollution anymore, because he says the technology is within sight to deal with it. Ford and other automakers are rolling out electric cars and are working on zero-emissions hydrogen fuel cell vehicles.

“I believe that in my lifetime, we’re going to largely solve the environmental impact of vehicles,” he said.

Still, serious traffic problems already exist in cities of fast-growing countries such as India and China. Ford says the problem will grow as population and incomes rise and more people buy cars.

Right now, there are 1.2 billion cars and trucks on the world’s roads, and another 144 million will be added in just four years, according consulting firm LMC Automotive in Troy, Mich. In China alone, annual auto sales will rise by more than 10 million — to almost 30 million — between now and 2016. In India, LMC says sales will nearly double in four years to over 6 million.

The solution, Ford says, is communications. That’s why he’s speaking to the Mobile World Congress, a conference for the cell phone and mobile device industry. The telecommunications industry likely will carry the data that will be used to solve the congestion problem.

He says technology is moving so fast that solutions already are starting to happen. In five or so years, more cars will have radar-based cruise control that automatically stops them from running into each other. More will have blind spot monitoring systems that stop cars from changing lanes if something’s in the way. By 2025, he sees cars using those features to communicate with each other, perhaps even taking over the driving in a traffic jam to find the best way out.

Beyond that, he sees “platooning” of cars that drive themselves, staying close together to get the maximum use out of highways. Cars also would park themselves close together to squeeze more use out of parking decks. Traffic lights would control the speed of cars to keep them moving through intersections. Governments would coordinate car travel with public transportation, and there would be more tiny cars that carry one or two people, Ford says.

With better coordination, the same number of people could travel in fewer buses, cars and trains, he says.

“”Even if the technology is there, there’s still going to have to be tremendous thought by urban planners,” he says.

Before his great-grandfather introduced the Ford Model T to the masses in 1908, Ford says few people traveled more than 25 miles from their homes. The car, he said, gave them the freedom to go anywhere. He says he’s trying to plan for congestion in order to preserve the freedom.

“That freedom has been threatened unless we redefine what personal mobility can be in a congested urbanized world,” Ford says.