Nearly three years after it was first mooted, the National Highway Traffic Safety Administration published a Notice of Proposed Rulemaking on Tuesday that will mandate vehicle to vehicle (V2V) communication systems in all new cars and trucks. Once the rule is finalized, car makers will have two model years to begin including V2V systems, with some added leeway for product cycles. V2V-equipped cars will communicate with each other at short ranges to prevent the kinds of accidents where current advanced driver assistance systems, most of which depend on line of sight, aren't effective.

V2V, and the related vehicle to infrastructure (V2I), relies on the Dedicated Short-range Radio Communication (DSRC) wireless protocol to communicate between devices at ranges of up to 984 feet (300m). Vehicles will be able to send out standardized "basic safety messages" that trigger driver alerts or even emergency avoidance actions to prevent crashes. (For a more detailed explanation of how V2V works, check out this piece from Ars' Sean Gallagher.)

Recognizing the immense implications of an insecure protocol, the notice asks industry and the public for input on the proposed security specifications and proposes that "vehicles contain “firewalls” between V2V modules and other vehicle modules connected to the data bus to help isolate V2V modules being used as a potential conduit into other vehicle systems." Privacy is also given due attention, and the proposed rule would prevent cars from sending out identifiable data like a vehicle's VIN or a driver's name or address.

It has taken a long time to get here—even longer than the 33 months we've waited to see the NHTSA's notice. The Federal Communications Commission set aside the 5.9GHz band for V2V and V2I back in 1999, although it took until 2002 before work began on the 802.11p protocol. Back then, a dedicated communications protocol seemed like a great idea since cell networks weren't thought capable of sufficiently low latency to be useful in this context. But nearly two decades later, it looks like 5G solves that problem, and you can bet that automakers will be packing 5G modems into cars as soon as they can get their hands on them. (With that in mind, the notice includes proposals for interoperability with non-DSRC protocols.)

As you might expect, companies with an interest in V2V technology are delighted. "As a leading technology provider to the automotive market, we view an accelerated rollout of this life-saving technology as one of the most important milestones in the history of our industry, one that will transform our roads and vehicles as never before," said Kurt Sievers of NXP (which makes a V2V system called RoadLINK).

Ravi Puvvala, CEO of Savari—which makes V2X systems—was similarly effusive: "V2X is clearly one of the big technology news stories of 2016 and this momentum will carry on into the New Year. This is one of those watershed moments that we will look back on fondly 10 or 20 years from now, examining how safe our roadways have become and how many lives were saved."

But not everyone is as enamored. Marc Scribner, a research fellow at the Competitive Enterprise Institute, worries that we're locking ourselves into an obsolete technology. "They're being a lot more conscientious about it than I think a lot of people give them credit for," he said. "I still think the technology is fundamentally flawed, and the way the rollout will happen is flawed, because there's very good odds that we'll have fully automated vehicles by the time this technology is deployed wide enough to give you any of these crash-avoidance benefits. You have to encounter another vehicle on the road with the technology for it to work."

"The latency problem that people were complaining about with regards to cell networks is going away," Scribner told Ars. "And you already have this widely deployed network that you're not taking advantage of; instead, you're talking about building an entirely new network—which no one knows how to pay for."

Interestingly, the V2I system that Audi demoed for us last week in Las Vegas uses 4G LTE and not DSRC to communicate between vehicles and traffic signals.

If you want to give NHTSA feedback on the proposed rule, the public comment period is open for 90 days.