EAST RUTHERFORD, NJ—We are traveling at an impossibly high speed along the Autobahn when a stalled Cadillac CTS looms ahead. As if sensing its plight, the Caddy's brake lights and backup lights flash. A warning flashes in my car's dashboard, the seat vibrates, and then powerful disc brakes bring us to a halt just a few feet from disaster—all without the driver touching a thing. The demo actually took place in the parking lot of Giants Stadium at about 20 mph, but one day it could happen on the Autobahn, or on Interstate 80, at serious speeds.

Okay, there could be some benefits from V2V early on: If every tenth car has V2V, and I come zipping around a bend and happen upon an auto accident just 30 seconds old, maybe one of the 10 cars that got there first has that transponder, my car slows automatically, and the cars behind me slow reflexively when they see my brake lights. But for everyday driving, the benefits just won't be there for a long time. And if you're an early adopter, you'll be broadcasting your position and speed to every car with a black-and-white paint scheme and a box of Dunkin Donuts on the passenger seat.

In comparison, drawing traffic flow information (as Inrix and Clear Channel do) from an increasing network of transponder-equipped vehicles makes sense, because knowing of delays far ahead is nice but not crucial, and if the information is incomplete, I'm no worse off than before.

So mark down V2V as a nice piece of research that might pay benefits in 15 years. I don't see many people rushing out to retrofit their cars with one-way transponders unless somebody pays for it (GM? The government?) . The short-term solution is active radar, laser, and sonar-based devices that get cheaper every year. Trickle-down theory, automotive style, means the safety gadgets of the rich and famous eventually make it to the mainstream consumer. Think airbags, anti-lock brakes, stability control, and side air curtains. Today, Cadillac; tomorrow, Chevy Cobalt.