With all the recent attention on self-driving cars
occasioned by the first fatality involving such vehicles, the advent of
"talking cars"—cars that communicate wirelessly via
vehicle-to-vehicle (V2V) communications—has taken a back seat, so to
speak. But V2V ultimately promises
to be a vital link in the chain of technologies that will make driverless
vehicles possible, as well as making ordinary human-driven cars safer.
The basic idea is this. Each V2V-equipped vehicle has a transmitter and receiver
that operate in a 5.9-GHz (microwave) wireless band. By one proposed standard, each car transmits its location,
speed, direction, and other relevant data ten times a second to any other car
in a thousand-yard (~910-meter) radius.
Other cars equipped with V2V can use this data to keep pace as a
following vehicle, or to avoid a collision with a car that is still out of visual
sight—around a corner, for instance—but on a collision course. Some government experts estimate that
if every vehicle on the road was equipped with V2V, the number of accidents not
related to impaired drivers (alcohol, etc.) could be reduced by as much as
80%. So what's the holdup? A
couple of things.
First it turns out that, according to a recent
Associated Press report, the main federal agency boosting V2V and prescribing
an industry standard for it is the National Highway Traffic Safety
Administration (NHTSA), which is now locked in a battle with another agency,
the Federal Communications Commission (FCC). The bone in this dogfight is the microwave band that V2V
needs to use. The FCC, leaned on
by powerful wireless-comm companies, wants to reallocate that part of the
spectrum for wireless internet users.
But a recent technical paper examined the tradeoffs involved in reducing
the bandwidth used by V2V, and showed that even the currently contemplated 75
MHz of spectrum might not be wide enough to allow virtually error-free
transmission, which is what is needed in this safety-critical application.
Aside from the radio-spectrum issue, there is a question
of security. The NHTSA has had enough
imagination to build in a complex security protocol for V2V. You can easily think of ways to use V2V
nefariously. For example, crooks
in an escape car being chased by cops could use a false V2V signal to tell the
cop car that it's about to have a head-on collision, and the cops would slam on
the brakes—if they trusted what the car told them. This assumes that the V2V information is used only as
warnings to the driver, but sooner or later automakers are going to take the
driver out of the loop and allow the V2V information to be used directly by the
car's control mechanisms—brakes, steering, accelerator, etc.
So in order to prevent such shenanigans, the NHTSA
has devised a complicated security system that involves digital certificates,
public-key infrastructure encryption, and a lot of other things that apparently
have never been combined in such an elaborate way before. It's nice that they have thought to
make each car anonymous and to ensure that potential hackers will have lots of
trouble hijacking the system, but even the NHTSA itself admits they haven't
worked all the bugs out of this security process yet.
The closest analogy I can think of between the
proposed V2V system and anything we have now is the air-traffic control system
that uses active transponders on each aircraft. The need for security in air-traffic control is a lot less,
because there are a lot fewer planes than there are cars, the Federal Aviation
Administration is looking over the airlines' shoulder all the time, and there
was already an extensive radar-based air-traffic control system in place before
the transponders were added. With
V2V, there is no centralized control, only a lot of cars talking with each
other, so the technical challenge is harder.
Even if the automakers started selling V2V-equipped
cars tomorrow, it would be twenty years, by some estimates, before nearly all
cars on the road would be so equipped.
And until then you couldn't count on doing things with V2V such as
traveling in closely-spaced packs or caravans on freeways, because even one
non-V2V car in the pack would throw everything off.
Still, if auto insurers find that V2V-equipped
vehicles really do get involved in accidents at a significantly lower rate,
they're likely to offer insurance discounts for such cars. And while consumer behavior is not
entirely predictable, buying a car that automatically lowers your insurance
rate would be a strong incentive for car buyers to upgrade to V2V sooner rather
than later. However, the insurance
companies aren't going to do that until they have a few years of data to base
their price tables on. And that
won't happen till there's a significant deployment of V2V-equipped cars. So we have a chicken-and-egg
problem.
Close to thirty years ago now, right after digital
ICs capable of generating voice-quality audio came out, the car makers
experimented with another kind of talking car. If you sat down and didn't fasten your seat belt, this
woman's voice came out of nowhere and nagged you to fasten it. That kind of talking car quickly
disappeared. The V2V idea shows
promise of making cars a lot safer without a lot of complexity added, except
for the system issues involved with spectrum allocation and security. I hope that the two fighting
executive-branch agencies can work out a reasonable compromise so that people
can both stream video as much as they want (or are willing to pay for), and
drive in safer cars. But so far,
we're not there yet.
Sources: The Associated Press
article "Auto tech industries clash over future of talking cars" was
carried in the print edition of the Austin
American-Statesman of Aug. 27, 2016, and appeared in other venues such as
the Aug. 25 online edition of the Los
Angeles Times at http://www.latimes.com/business/autos/la-fi-hy-talking-cars-20160825-snap-story.html. I also referred to a technical paper by
Lei Shi and Ki Wong Sung, "Spectrum Requirement for Vehicle-to-Vehicle
Communication for Traffic Safety," available at https://www.metis2020.com/wp-content/uploads/publications/VTCSpring_2014_Shi_etal_SpectrumRequirementForV2VCommunication.pdf,
and articles on V2V security at https://www.contrastsecurity.com/security-influencers/v2v-communications
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