The auto industry is promising to dramatically expand “vehicle-to-everything” communication technology, but only if the Federal Communication Commission rolls back its decision to take away the current airwaves dedicated to that technology.

Vehicle-to-everything (V2X) technology is expected to increase road safety by allowing vehicles to communicate with one another, as well as smart infrastructure like traffic signals, to better avoid crashes or other mishaps. The Alliance for Automotive Innovation, a trade group that represents all of the major automakers and their suppliers, released a statement Thursday vowing to install 5 million pieces of V2X equipment over the next five years. But that promise was predicated on the FCC reversing an earlier decision to repurpose the airwaves that have been set aside for V2X communication.

“This commitment represents more than 50 times the number of devices on the road today,” said John Bozzella, the group’s president, in a statement. “This commitment by automakers clearly shows that these lifesaving technologies are ready and can be deployed in significant numbers in the next five years.”

In 1999, the FCC agreed to set aside 75 megahertz of spectrum in the 5.9 gigahertz band for something called Dedicated Short Range Communications (DSRC) services, which would be used to improve road safety through V2X technologies. Broadly speaking, V2X allows vehicles to send and receive messages about road conditions, like speeding cars, weather, or traffic congestion. It could also help prevent crashes by using that information to make decisions, like applying emergency braking.

Some experts say the wide deployment of the technology could help speed the adoption of self-driving cars, which could use vehicle-to-vehicle (V2V) communications to bolster their ability to “see” their environment and make better driving decisions.

But the auto industry was slow to develop V2X technology, and the rollout has been piecemeal. Mercedes installed V2V equipment in both the 2017 E-Class and 2018 S-Class. General Motors also introduced V2V in the Cadillac CTS in 2017. Other automakers began looking closely at a newer technology called cellular V2X (C-V2X), using existing cell networks to send communications.

In 2017, the Trump administration announced that it was killing an Obama-era mandate that would have required new cars to be equipped with V2V technology. And last year, tensions escalated when the FCC put out a new plan to use some of the spectrum set aside for V2X to expand Wi-Fi instead. Calling V2X “a promise unfulfilled,” FCC Chairman Ajit Pai proposed to make the lower 45MHz of the band available for unlicensed uses such as Wi-Fi and allocate the upper 20MHz for C-V2X.

Automakers lobbied against the decision, arguing that allowing Wi-Fi to use parts of the spectrum would interfere with connected car technology. Now the industry is vowing to increase its deployment of V2X technology, but only if the FCC walks back its decision to reallocate portions of the spectrum.

In a statement, the FCC said the auto industry’s promises were in effect too little too late. “Given that about 17 million new vehicles have been sold in the United States in each of the last five years, this is not an impressive commitment,” an FCC spokesperson said in an email. “Instead, it only reinforces the need for the FCC to reform the use of the 5.9 GHz band so that it is put to its best use for the American people.”