The Federal Communications Commission voted Wednesday to open a new chunk of the airwaves for wireless Internet, a step designed to immediately make it easier for people to get online but which critics say could imperil future highway safety technology with the potential to save thousands of lives a year.

The airwaves at issue have been dedicated to highway safety since 1999, with the idea that they could be used for vehicles to send warnings to one another or let firetrucks turn traffic lights green as they speed to an emergency.

But the safety band, as the airwaves are known, has yet to live up to that promise. And FCC Chairman Ajit Pai said the coronavirus pandemic has underscored the need for people to have reliable Internet access at home.

“This FCC unlike its predecessor is not going to kick the can down the road any longer,” he said.

The five-member commission’s two Democrats used a maneuver that allowed them to withhold full support for the measure without voting against it, referring to a last-minute letter by a leading Senate Democrat asking the commission to delay until the new Congress and presidential administration are installed.

Pai dismissed such calls for more time as “performative.”

The commission’s approach had the support of wireless Internet providers and others in the technology industry, but also faced determined opposition from a coalition of automakers, highway safety advocates, members of Congress who oversee transportation and Transportation Secretary Elaine Chao.

“The FCC has just been full speed ahead, and we’re not going to worry about data or what safety experts are saying,” said Shailen Bhatt, the chief executive of the Intelligent Transportation Society of America.

The original safety band consisted of 75 MHz of spectrum for vehicles to be able to share messages using a technology called dedicated short-range communications.

The FCC’s action Wednesday will make two major changes: It will take away 45 MHz from auto safety and open it up to uses like WiFi and wireless broadband, and it will allocate the remaining 30 MHz for a new connected-vehicle standard known as cellular vehicle-to-everything or C-V2X.

The plan to change how the spectrum is allocated has created divisions within the federal government.

In an internal memo, a Treasury official raised concerns about the FCC’s decision. The official wrote that it would seem to do little to improve Internet access and put the United States at an economic disadvantage with China, which is also developing connected-car technology.

And in a recent letter, Chao wrote that the FCC’s approach put her department’s efforts to reduce traffic deaths “in peril.”

“The Commission’s benefit-cost analysis is also fatally flawed,” Chao wrote, arguing the that it had underplayed the safety benefits of connected-car technology while discounting the costs of switching to new technologies.

On Tuesday, Sen. Maria Cantwell (Wash.), the top Democrat on the Senate Commerce Committee, pointed to the concerns among other government agencies in a letter to Pai, asking him to delay the vote.

“The FCC’s public interest obligation demands that the FCC take the necessary time to ensure that its spectrum allocation actions do not compromise safety and the greater public welfare,” Cantwell wrote.

Opponents of the change could yet mount a challenge to the FCC in court, advancing arguments like Chao’s that the commission failed to follow the proper procedures.

While progress on making use of the band has been slow, in recent years state and local transportation agencies have been experimenting with the technology, and there are now about 75 underway, with more in planning phases, according to the Transportation Department. The department is backing pilot programs in New York City, Wyoming and Tampa with $45 million.

In Salt Lake City, buses that are running late have been able to communicate with traffic lights to keep them green long enough to get back on schedule. And the New York project includes about 2,000 vehicles with the ability to share safety messages, and hundreds more roadside systems.

Under the new FCC rules, those projects would have to wind up or shift to the new C-V2X technology.

Although some airwaves will continue to be set aside for road safety uses, opponents of the change say there is a risk that wireless devices will cause interference and that with a smaller band some proposed technologies won’t function, putting lives at risk.

For example, Continental Automotive Systems, a parts manufacturer, wrote in a submission to the FCC that techniques like allowing one car to warn another about the location of a pedestrian, or for vehicles to let one another know where they’re about to drive, won’t function in a narrower slice of the airwaves.

And yet, the company acknowledged those technologies are still at least four years away. But existing Internet hardware could be quickly adapted to make use of the new spectrum.

As the pandemic took hold and more people began working from home, the FCC began temporarily opening up parts of the band to wireless Internet providers. The commission says it has issued more than 100 approvals and that rural areas in particular stand to benefit from the airwaves being opened up.