AUSTIN - At the beginning of the century, pundits warned of "peak oil," the idea that the world was running out of accessible crude. Petroleum engineers solved that problem.

Lately, energy companies have debated "peak demand," the prediction that the world's thirst for petroleum will slake. Estimates for when this might happen range from 2025 to 2040.

A new way to forecast peak demand is to think about "peak car," the date when the number of automobiles on U.S. roads begins to drop. Based on what I heard at the University of Texas Energy Week in Austin, there are substantial efforts to hasten that day.

America's love affair with the automobile is powerful. For people of middle age and older, such as myself, owning a car was an extension of the old Texas aphorism: "A man without a horse ain't no man at all."

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Financially, though, individual car ownership makes little sense. The average American spends $7,000 to $10,000 a year on a vehicle that sits idle 94 percent of the time. Even today there are more economical options to owning a car. The UT Energy Institute has developed a tool to calculate your costs at rideordrive.org/calculator.

Logically, we can all understand that not everyone can, or should, drive alone in their personal vehicles. Cities are reaching capacity, said Rob Spillar, director of transportation for the City of Austin.

"We have to get more people out of their single-occupancy vehicles," he said. "Just from a mathematical and economics perspective, if a major employment center is to double in activity levels over the next 20 years ... we have to do something different."

While public transportation has its place, autonomous and electric vehicles could offer better and more affordable solutions, according to the Rocky Mountain Institute. By getting rid of the driver and using electricity instead of gasoline, the cost of a mile traveled in a taxi drops from $2 to less than $1, the institute's research found.

Developing these technologies, and getting costs down, is a top priority for transportation network companies, said Aaron Fox, general manager for Lyft in Central Texas.

"We know exactly where and when people need rides," Fox said. "There is an incredible amount of system optimization we can do if we had our own fleet. That's a little farther in the future, but that's where the big prize is."

Experts believe that autonomous vehicles will use roads 30 percent more efficiently than human drivers. Commuters in 2035 can also cut travel costs in half by using autonomous and electric taxis instead of personal cars, the Rocky Mountain Institute calculated.

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Using such vehicles could reduce the number of cars on the road by 50 percent to 80 percent, several studies calculated.

To discourage single-occupant vehicles and encourage people to use alternatives, some European cities have already banned personal, gasoline-fueled vehicles in downtown areas. Congestion charges, fuel taxes and tolls are other tools city officials are using to change behavior. More will come to Texas eventually.

General Motors is already experimenting with supplying shared electric vehicles as a transportation service, called Maven, rather than selling them as a product, said Alex Keros, smart cities chief at GM's Urban Mobility. GM offers electric Chevy Bolts to Uber and Lyft driver in San Francisco as weekly rentals.

"We are committed to electrification," Keros said. "Putting these pieces together have some neat multiplier effects."

About 71 percent of the oil consumed in the U.S. is used to make liquid fuels for transportation, according to the Energy Information Administration. Cheaper electric cars have raised concerns that total oil consumption could go down as early as 2025.

Royal Dutch Shell is preparing for a world with lower oil consumption, focusing more on ways to generate electricity, said Ajay Mehta, general manager for long-range research and new energy technologies at Shell.

"I think the world has changed in ways that are irrevocable," he said. "We view this as a fundamental disruption of the energy system, and we don't want to be a bystander."

The Rocky Mountain Institute believes peak car demand could come in 2020. I think that's too soon, but with autonomous and electric vehicles on the road today, no one knows for sure.

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Surveys show that younger adults understand the financial liability of auto ownership, which explains the use of transportation networks. Millennials are the largest generation living in the U.S., and their consumer choices will impact all of us.

Houstonians who depend on the energy business should watch these trends closely. Because when consumers begin abandoning their cars, they will be abandoning oil too.