(Bloomberg) – General Motors Co. is rolling out a sedanladen with gadgets that track other cars on the road and canautomatically brake to avoid collisions,fulfilling a safety vision decades in the making.

Yet the 2017 Cadillac CTS arrives to skepticism inWashington, where Detroit's dream of cars talking to cars isrunning into Silicon Valley's wireless aspirations.

Tech companies want to claim some of the airwaves dedicated tothe car-safety systems 17 years ago, long before smartphones andmobile apps sparked a rush for new frequencies. That would mean GM,Toyota Motor Corp. and other automakers could be forced to sharethe frequencies.

The rivalry shows how growing demand for mobile airwaves isupending what once were communications certainties. U.S. mobiledata traffic tripled from 2013 to 2015, according to CTIA, awireless trade group. According to a forecast by CiscoSystems Inc., U.S. mobile data traffic will grow six-fold by2020.

Safety, entertainment

Carmakers say unfettered use of the airwaves is needed to assuresafety.

Dividing the airwaves may invalidate industry testing alreadydone and “delay the deployment of life-saving technologies,” saidAnnemarie Pender, spokeswoman for the Association ofGlobal Automakers, a Washington-based trade group representing14 car companies including Toyota and Honda Motor Co.

“Our view is that safety delayed is safety denied,” Pendersaid.

But critics contend Detroit also wants to provide servicesalready available on smartphones — including entertainment,traffic warnings, and mapping.

“The auto industry has been very successful in pitching this asbeing about our great concern for life and safety, while these guysjust want you to stream cat videos and Netflix while you're in yourcar,” Harold Feld, senior vice president at the policy group PublicKnowledge, said in an interview.

The Federal CommunicationsCommission is examining ways to share and expects to finishtesting in January. A final decision won't come until after moreconsultations with safety regulators at the TransportationDepartment.

Carmakers say they need all the airwaves the federal governmentgranted them in 1999, but may be able to share some as long assafety isn't disturbed. They say changes may cause delay.

Finite resource

“We get that spectrum is a finite resource, and there isn'tenough to go around,” said Hilary Cain, director of technology andinnovation policy at Toyota in Washington. “At the same time, weare very, very, very committed to vehicle-to-vehicle communication,so we're concerned about finding the right sharing solution thatdoesn't upend our technology at this stage of development.”

Several proposals have evolved to address the dispute. One fromCisco that's backed by the auto industry calls for sharing theairwaves but prioritizing car-safety communications. Qualcomm Inc.has proposed a rival strategy of restricting basic safety functionsto part of the airwaves, and letting cars and smartphones share onan equal footing elsewhere — an approach backed by some techpolicy groups.

Prioritize car safety

GM knows the vehicle-to-vehicle technology in the 2017 Cadillacswould work under the Cisco protocol, which doesn't change thechannel configuration, said Harry Lightsey, executive director ofglobal connected customer experience for the Detroit-basedautomaker. It's not sure the Qualcomm proposal would work.

“We're putting hardware into vehicles based on the currentchannel configuration,” Lightsey said in an interview. “All of thathardware would have to be changed. That's obviously a concern.”

The Information TechnologyIndustry Council, with members including Qualcomm, Google,Facebook Inc., Twitter Inc. and Amazon.com Inc., favors sharing theauto airwaves, the Washington-based trade group said infilings.

Talking cars

As wireless use grows, the radio spectrum is being re-jiggeredto make room for the deluge of video, texts, talk andmachine-to-machine communications. TV broadcasters are surrenderingairwaves for use by smartphones, and large telecommunicationsproviders AT&T Inc., Verizon Communications Inc and T-Mobile USInc. are digging into their treasuries to buy access to morefrequencies. Smaller players, too, see opportunities: GlobalstarInc. and Ligado Networks, the former LightSquared, want to letsmartphones use frequencies now devoted to satellites, and are inline for a rich payoff if they get permission from the FCC.

Related: The connected car — from threat toopportunity

Talking-car technology is arriving at this time of ferment. Itfeatures vehicle-to-vehicle communications over radio signals witha range of about 300 meters. Uses include warnings about impendingcollisions at intersections, sharp curves and blind spots. Theinformation stream would, for instance, warn drivers not to changelanes or attempt to pass if there's an oncoming truck.

The same airwaves can supplement current Wi-Fi frequencies,which are becoming overloaded and sluggish. That makes thetalking-car frequencies an object of desire for tech companies,which prosper as web use grows, and for cable companies, whichinvite subscribers to watch video on tablets and other devices, notjust TV sets. No. 1 U.S. cable provider Comcast Corp., forinstance, has 14 million Wi-Fi hotspots.

Testing for interference

Radio signals can reach through vehicles and around corners,unlike some sensor-based technologies coming out on current models— such as the car being tested by Alphabet Inc.'s Google. Thatvehicle doesn't use the airwaves in question, and relies on maps,lasers, radars and cameras.

Three of the FCC's five commissioners put out statements backingairwaves sharing when the agency announced its testing plan June 1.On Monday, Commissioner Jessica Rosenworcel, a member of theagency's Democratic majority, wrote that the talking-car airwavesrepresent “a golden opportunity” for more Wi-Fi.

“We need to test to make sure introducing Wi-Fi in theseairwaves will not impact roadway safety — and we need to getthis testing underway as soon as possible,” Rosenworcel said in thearticle on the website of Morning Consult, a media and technologycompany.

“It is very encouraging that the FCC is moving ahead” withtesting, said Michael Calabrese, director of the Wireless FutureProject at the Washington-based New America policy group.

Switching frequencies

Members of the Alliance ofAutomobile Manufacturers, including Toyota and GM, have toldthe FCC that carmakers need interference-free access to all theallocated spectrum. Wi-Fi devices could switch to other frequencieswithin thousandths of a second, and usually cars won't precludeother users, said Mary Brown, senior director of spectrum andtechnology policy at Cisco.

“There's going to be a lot of spectrum available all the time inmost places,” Brown said in an interview.

Changes like those sought by Qualcomm would require new testingthat would slow deployment, the automakers and Cisco said inmeetings with FCC officials.

Not so, according to Dean Brenner, senior vice president forgovernment affairs at Qualcomm. “We don't see it as causingsignificant delay,” Brenner said in an interview.

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