V2V: Vehicle-to-vehicle communication

On The Road To The Self-Driving Car | On Point with Tom Ashbrook:
"The National Highway Traffic Safety Administration said Monday it will soon require all new cars to talk to one another.  Share location, speed, direction and more, electronically.  Vehicle-to-vehicle – “V2V” – communication.  Right behind that comes the next frontier:  self-driving cars.  First they talk to one another, next they drive themselves.  The auto industry, Google, and the law are all gearing up."

Surprise: ‘Vehicle-to-Vehicle’ Communication Is Already Here | On Point with Tom Ashbrook
"They are literally talking about being able to transit ten pieces of data every second. And it will be everything from your car position, via GPS, to how well you brake, how well you are braking, are you hitting ice, are you turning left are you turning right, are you speeding — all of that information constantly transmitted in a radius of about 300 yards or so, maybe more, and other cars in the vicinity picking up all that information. It all amalgamates in each other’s computers and the cars..."

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This information could also be used to adjust traffic lights to improve throughput, for example, and traffic signs including traffic lights could also transmit info to cars, or even mobile phones / devices in the cars.

Why not use existing mobile devices and mobile networks to "enhance driving?" To some extent this is already happening, since traffic information on Google maps is partially based on info from mobile devices...