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Getting Out of the Heat
Traffic congestion "temperature" could help drivers avoid delays.
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The Weather Channel has brought to forecasting weather what a
Georgia Tech researcher hopes to bring to predicting traffic congestion.
image courtesy of
John Leonard
Dr. John Leonard has
created a "star diagram" that Web surfers can view to obtain travel time
estimates under current traffic conditions.
People plan their days according to the weather forecast, but
they can't do that with traffic — at least not quite yet, says Dr. John
Leonard, an associate professor in the School of Civil and Environmental
Engineering.
Leonard is developing a cutting-edge model that uses data from
traffic surveillance systems — such as the 300-plus video cameras
installed on freeways in Atlanta — to make real-time decisions on
operations of a highway corridor or region. He calls it a real-time
"temperature," or index, of traffic congestion.
"People need a simple-to-understand number — even if it doesn't
have a physical meaning — to represent traffic congestion," Leonard
says. "We need to publicize it daily so people start to develop a
personal understanding of congestion and plan accordingly."
To create the congestion index, Leonard is developing ways to
collect traffic volume data from the
Georgia Department of Transportation's video
surveillance system in Atlanta and from commonly
used loop detectors on roadways. Then he can develop traffic flow models
to synthesize historical and current measures of delay, such as speed,
travel time or density, that in combination represent congestion. Once
he achieves that feat, his next step is developing a traffic congestion
forecast for the next day, based on existing conditions and special
events.
"Many people have the flexibility to plan their trips according
to traffic congestion," Leonard says. "People make a lot of
discretionary trips to the store, and there are a lot of courier trips
that could be rescheduled."
Publicizing the traffic congestion index will be key to its
having the intended effect. Leonard envisions freeway message board,
radio, television and Web site distribution. Web site users could select
one of several points of origin and get a real-time "star diagram" that
would show them graphically an estimated travel time to any of the
various points of the "star."
Besides the obvious short-term benefits of a traffic congestion
index, long-term benefits would include better traffic planning for the
future. This information should also be integrated with ozone
forecasting, work that is also ongoing at Georgia Tech, he adds.
By this summer, Leonard expects to have developed a prototype
traffic congestion index, which he will demonstrate to Georgia DOT
decision makers. Full implementation of the traffic congestion index is
probably several years away, Leonard adds. Though Atlanta will be the
testbed for the index system, it could be implemented anywhere.
Meanwhile, Leonard's other research focuses on traffic signal
coordination. He develops standard plans for optimal timing of signals.
"How do we look at what's going on in a travel control system in terms
of traffic, the capabilities of the hardware and the drivers, and then
develop ways to coordinate the street lights so drivers can hit the
green and hit the green and so on?" Leonard asks. "There are a lot of
impediments to that, some technical and some non-technical. Developing
tools and strategies for the traffic engineers to coordinate signals is
my goal."
The research involves collecting data from a variety of sources
and integrating it into a data set. Then Leonard develops traffic flow
models and computer programs to evaluate that data and prepare a
coordinated timing plan. "There isn't just one best timing plan,"
Leonard notes. "There are a lot of different strategies that are
appropriate in different situations. It's almost an art. We train
traffic engineers in that art."
Signal coordination plans are in place in cities almost
everywhere, despite what drivers might think, Leonard says. "The problem
with the existing infrastructure is that it doesn't respond well to
change," he explains. A special event or car stall can negate the
effects of signal coordination. Research is now under way elsewhere to
develop signal coordination plans that respond in real time to such
changes in traffic flow.
— Jane M. Sanders
For more information, contact Dr. John Leonard, School of Civil and
Environmental Engineering, Georgia Institute of Technology, Atlanta, GA
30332-0355. (Telephone: 404/894-2360) (E-mail:
john.leonard@ce.gatech.edu)
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