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We have
all been there, out on
the road, stopped in
traffic with no apparent
reason for the delay.
The hard truth is bad
news. What is
causes the traffic jams
is too much traffic.
 An
accident? Construction
work? A bottleneck? No,
just too much traffic
Institute
of Physics’ New Journal
of Physics New Journal of
Physics
March 2008
A new study from a
Japanese research group
explains why we’re
occasionally caught in
traffic jams for no
visible reason. The real
origin of traffic jams
often has nothing to do
with obvious obstructions
such as accidents or
construction work but is
simply the result of
there being too many cars
on the road.
The research,
published March 2008 in
the New Journal of
Physics, shows how
model patterns, normally
used to understand the
movement of many-particle
systems, have been
applied to real-life
moving traffic. The
research shows that even
tiny fluctuations in
car-road density cause a
chain reaction which can
lead to a jam.
The research found
that tiny fluctuations in
speed, always existing
when drivers want to keep
appropriate headway
space, have a cumulative
effect. Once traffic
reaches a critical
density, the cumulative
effect of gentle braking
rushes back over drivers
like a wave and leads to
a standstill.
The researchers in
Japan used a circular
track with a
circumference of 230m.
They put 22 cars on the
road and asked the
drivers to go steadily at
30km/h around the track.
While the flow was
initially free, the
effect of a driver
altering his speed
reverberated around the
track and led to brief
standstills.
Yuki Sugiyama,
physicist from Nagoya
University, said,
“Although the emerging
jam in our experiment is
small, its behaviour is
not different from large
ones on highways. When a
large number of vehicles,
beyond the road capacity,
are successively injected
into the road, the
density exceeds the
critical value and the
free flow state becomes
unstable.”
The researchers will
be advancing their
research by using larger
roads and more vehicles
to further test their
findings.
The research suggests
that it might be possible
to estimate critical
density of roads, making
it possible to build
roads fit for the number
of drivers needing use of
it or, on for example
toll roads, only allowing
the right number of cars
access to the road to
stop mid-flow traffic
jams.
All materials courtesy
of the
Institute
of Physics’ New Journal
of Physics New Journal of
Physics
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