http://www.dailycal.org/particle.php?id=19463
Sci-Tech
Wireless Sensor Could Reduce Traffic Congestion
BY Omeed Elboudwarej
Contribution Writer
Wednesday, September 14, 2005
Commuters often complain of the ubiquitous presence of traffic in
California. Fortunately, a new system of wireless road sensors may
improve traffic monitoring systems by replacing current loop
detectors and reducing traffic congestion.
To effectively manage and operate a freeway, an accurate minute-by-
minute monitoring of traffic conditions is important in predicting
real-time traffic conditions and guiding policies concerning
renovations of existing roads.
Transportation departments at the federal and state levels get their
traffic data from hexagon-shaped wire sensors called loop detectors
that are embedded in roadways every third of a mile. With as many as
25,000 loop detectors in California alone, these sensors provide real-
time freeway figures every 30 seconds, such as how many vehicles pass
over each loop and the average time a vehicle is on the loop.
“Typically 30 to 50 percent of loop detectors don’t last ten years
like they are expected to,” said Pravin Varaiya, professor of
electrical engineering and computer science at UC Berkeley and
researcher with the Center for Information Technology Research in the
Interest of Society. “Given that this is the only source of data we
have, the loop detector system must be replaced with something that
is more cost-efficient and reliable.”
Varaiya began investigating the possibility of using wireless sensors
as a possible replacement to the faulty loop detectors in 2002 while
working with the Freeway Performance Evaluation Monitoring System, a
California web-based tool that aggregates data from California’s
major metropolitan areas in order to analyze traffic patterns and
monitor freeway operations.
The result of three years of research is a wireless sensor designed
by Varaiya and his colleagues that is approximately four inches in
diameter and contains a magnetic sensor, computer processor, short-
range wireless radio, and a battery that lasts up to ten years. A
steel cover strong enough to endure heavy car loads encases the
intricate components.
These sensors can be glued onto the surface of the road in the same
manner as reflector studs, an attractive alternative to the costly
replacement of loop detectors that requires sawing through road
pavement and reconnecting circuit wires. However, the team also
created an underground wireless sensor that is half the size of its
above-ground counterpart for installation in roadways prone to heavy
snowfall. Snow ploughs would tear exposed sensors off the pavement.
Small base stations located roadside collect the data from the
information relayed by the radios in the sensors and deliver it via a
cellular network to the Traffic Management Center at Caltrans.
The team adopted a sensing model based on magnetic fields rather than
a less-accurate acoustic system that could not distinguish which lane
a vehicle was driving in or the type of vehicle.
“As a vehicle goes over the sensor, there is a localized shift in the
earth’s magnetic field because of the presence of iron on the
vehicle,” Varaiya said. “This shift is detected by the magnetic
sensor and recorded by the processor.”
The sensor identifies specific types of cars since the distribution
of magnetic material varies between a bus, car, motorcycle or truck.
This information helps transportation divisions ascertain how to best
reduce road congestion and identify roadway deficiencies.
According to Varaiya, the availability of more accurate and detailed
traffic data could cut congestion rates in high-traffic areas by as
much as 50 percent. In addition, the wireless sensors are predicted
to cost one-third of the roughly $50,000 spent installing a loop
detector system across an eight-lane stretch of the freeway.
“Accurate measurements of what is happening on roads are crucial for
the future because we cannot keep expanding freeways to deal with the
problem of growing traffic,” Varaiya said. “If in use, these wireless
sensors will help make such expansions a thing of the past.”
Contact Omeed Elboudwarej at [EMAIL PROTECTED]
(c) 2003 The Daily Californian
Berkeley, CA
[EMAIL PROTECTED]
Printable URL: http://www.dailycal.org/particle.asp?id=19463
Original URL: http://www.daiylcal.org/article.asp?=19463
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