I have long believed that we will never be able to build roads quickly
enough to cure today's traffic congestion, let alone add enough
capacity to meet tomorrow's new demand. Road building costs too much
money and takes too much time. But what DOES have a chance of working
is technology which allows our cars to coordinate amongst themselves,
not only improving safety but efficiency as well.

http://members.forbes.com/forbes/2007/0129/052.html

Cadillacs, Camrys and Accords will soon be chatting on the causeway.
Will this keep them from crashing into one another?

On a general motors test track in Warren, Mich. an engineer sitting in
the passenger seat of a black Cadillac CTS gives a reporter the
following instructions: Step on the gas and drive 30mph toward another
CTS parked in the same lane. Don't touch the brakes.

Two car lengths before a nasty collision, and just before panic sets
in, the two Caddies start talking to each other, sharing status
reports over tiny radio chips in their trunks. The moving CTS realizes
it has to brake, and does so all by itself.

These cars are test vehicles in General Motors (nyse: GM - news -
people )' effort to develop vehicle-to-vehicle communications systems.
Other automakers are developing similar systems in the hope that,
starting five years from now, roads and highways will be
information-rich networks, with cars knowing what other cars are doing
and responding intelligently. "It opens up a whole new world for
automotive safety," says GM's advanced-technology chief, Larry D.
Burns. "A road where cars wouldn't potentially crash at all."

For $200 per vehicle--the cost of a Wi-Fi router, a microprocessor and
a global positioning system chip--cars will be able to continually
share data about their location, speed, angle of steering wheel,
acceleration or deceleration rate, even whether the air bags have gone
off or the windshield wipers are on. With help from signals from
roadside markers and traffic lights, in-car computers will be able to
determine if a car should slam on the brakes, alert the driver to a
passing vehicle in the blind spot or slow for a red light up ahead
that another driver isn't heeding.

"No longer are we only reacting to what has already happened. We are
anticipating," says Kenneth Laberteaux, a Toyota (nyse: TM - news -
people ) researcher developing such technology at the company's Ann
Arbor, Mich. technical center.

The automakers still have a mountain of issues to sort out, including
how to rank incoming signals by importance, how to minimize false
alarms and how to make the networks secure. Automakers don't want a
roadside hoodlum to be able to bring traffic to a halt with a push of
a button.

GM, Toyota and others are toying with ideas such as cockpit-style
displays that show icons of cars that pose a threat; audible signals;
and vibrating seats and steering wheels. When a wired car is in the
blind spot of one of GM's test Cadillacs, an icon of a car lights up
in the side mirror. If the driver puts on the turn signal anyway, the
seat vibrates.

The hard part for now is designing the software that will process the
kind of data volume that a congested interstate interchange could
produce. GM has had five software engineers working for about two
years to write the controlling software, now up to 4,000 lines of
instructions.

At first the networks will be about as useful as the first few e-mail
accounts were. But even with networking features installed in 7% of
the 241 million cars on the road, manufacturers say there will be big
safety improvements. "To some people, driving is the distraction: They
want to comb their hair, they want to drink their coffee, they want to
talk on their cell phones," says GM's Burns.

Drivers would be able to choose their level of protection, and
carmakers could compete on which model's networking features are the
most elaborate, just as they do now on the number of air bags or
navigation system features.

The auto companies are meeting weekly to develop standards. Systems
being tested now have a range of 750 feet and share data packets 140
bytes long (the equivalent of a few typed sentences) every tenth of a
second. Car computers keep a record of the activities of all
surrounding cars so they can quickly discard information about a car
moving quickly in the opposite direction but track a car moving in the
same direction around a corner and determine if it will soon be in the
same lane as your own. Carmakers are also working with the U.S.
Department of Transportation, which is testing applications through
which vehicles would communicate with signals and road signs.

The first networks will work among cars in close proximity, but
automakers hope eventually to enable critical signals to bounce
rapidly down the highway from car to car to car, so-called multihop
messaging. That way vehicles a mile back from an accident would know
immediately of trouble ahead.

All this networking was made possible by a 1999 grant from Congress to
the auto industry of 75 megahertz of radio spectrum for safety use.
State and federal transportation departments also would like to use
the systems to gather information from the highways. If 90% of cars on
one stretch of highway have their wipers on full blast, they could
know it's raining heavily. That could make traffic reports, now
gathered haphazardly by am radio stations, far more precise.