Utah officials have long planned billions of dollars more of mass transit in coming years — saying it’s the best way to handle expected rapid growth in crowded valleys where not many more freeways are possible, and that it could cut pollution.

But a task force planning Utah’s future transportation heard a contrary opinion Wednesday — arguing against more TRAX, FrontRunner or streetcars because self-driving, Uber-style shared taxis may make rail transit obsolete.

“I think automated vehicles sometime in the future will be what you may call a transit killer in all but the densest urban cores,” testified Marc Scribner, senior fellow at the Competitive Enterprise Institute, a Washington, D.C., think tank that promotes limited government and free enterprise.

He told the Transportation Governance and Funding Task Force that when such self-driving cars offer swift and cheap service door to door, few will prefer “slow-moving mass transit.”

Such automated cars may be available relatively soon, he predicts.

“By 2030, we may have automated, self-driving cars. What do we do with new rail that may be coming online in 2025? Well, we’re stuck with that until mid-century at least,” and low ridership that may make paying off bonds difficult, he said.

State Sen. Wayne Harper, R-Taylorsville, co-chairman of the task force, said many in Utah argue that more TRAX and surface rail systems are indeed needed and are included in long-range plans. He asked Scribner what he thinks of that.

“I think that would be a mistake,” he said. “Decision-making currently unsupported by the best available evidence will look downright disastrous in the coming decades once automated vehicles are widely deployed.”

Scribner added, “In recent decades, many U.S. cities including Salt Lake City have developed costly, inefficient surface rail transit systems, such as light rail and streetcars. The cost of surface rail transit far exceeds that of buses, even bus rapid transit with dedicated lanes, while the benefits are few relative to the cheaper alternatives.”

Studies show rail lines may attract some moderate economic development on their routes, he said. However, Scribner dismissed that as just moving construction that would have occurred somewhere else in the same metro area.

He argued that buses bring as many transportation benefits as rail, and are cheaper and more flexible — which may make them a wiser investment for a future with many unknowns.

If higher quality transit is still desired, Scribner said, “bus rapid transit may be the way to go.” It is sort of a TRAX on wheels, often with street lanes reserved for buses. One such line operates in West Valley City, and another is under construction in Provo and Orem.

“If automated vehicles take over the world,” Scribner said, government could return the dedicated bus rapid transit lanes back to general traffic — something not easily done with more expensive and permanent rail tracks.

“For the sake of reducing the risk of public investments, I caution strongly against additional surface rail transit investments,” he said. “Where rail transit makes most sense is where you have very, very high population density, and at that point you put it underground, you don’t have it on the surface.”

He added that likely makes sense only in a few large cities, such as New York City — not the Wasatch Front.