Adaptive cruise control systems work by monitoring the road ahead
using a radar or laser-based device and then use both the accelerator
and brake to maintain a certain distance from the vehicle ahead.
(Other variations can bring the car to a halt in the event of a potential
accident).
These devices have been available on upmarket cars for ten years
or more and are now becoming increasingly common. If you drive
regularly on freeways, the chances are you regularly come across
other vehicles being driven by these devices, especially in Europe
and Japan (here, the density of traffic means that ordinary cruise
control has never caught on in the way it has in the U.S.).
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So how does the presence of computer-controlled vehicles affect traffic
dynamics? Today, Arne Kesting and pals at the Technical University of
Dresden in Germany provide an answer of sorts using a model of
traffic flow in which both human and computer-driven cars share the
road.
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They say that the presence of computer-driven cars increases the
amount of traffic that can flow on a road before jamming occurs. And
the more of these cars, the greater the capacity becomes. “1 percent more [computer-controlled] vehicles will lead to an increase of the
capacities by about 0.3 percent,” they say.
That’s interesting but there have been other studies suggesting
that computer-controlled cars can lead to greater congestion and
it’s not at all clear why Kesting and company’s analysis is superior.
Either way, the argument is probably moot. Computer-controlled cars are just
the first step in what many expect to be a revolution in car travel.
The big increases in traffic capacity are likely to come when cars
are able to communicate with each other. This should allow entire
platoons of vehicles to travel as one unit, with just a few
centimetres gap between cars and the vehicle in the front communicating its intentions to all the others. Platooning should improve fuel
efficiency, too.
Of course, that won’t be possible until there is a critical mass
of computer-controlled cars on the roads. Even then there is a bigger
hurdle to overcome of creating the legal framework in which all this can happen: imagine the insurance claims if one of these
platoons were to crash.
The biggest challenge for the makers of cars that drive themselves
is no longer technical but legal.
Ref: arxiv.org/abs/0912.3613: Enhanced Intelligent Driver Model to Access the Impact of Driving Strategies on Traffic Capacity
