Crash
course
By
Tai Viinikka
Secretly, most of us think we’re great drivers.
Whether we are aggressive or cautious, we assume the roads would
flow smoothly, and traffic jams would be a rare marvel, if only
everyone drove like, well, like me. Like many secret vanities, this
one is just not true, and traffic researchers have built computer
models that prove it.
A new approach to modeling, in which individual simulated drivers
make individual simulated decisions, began in the 1990s. These driver-behavior
models are reaching maturity now, and their proponents say that
even the most vexing and perplexing aspects of traffic can be predicted
and even understood.
Models that follow individual vehicles are already beginning to
make useful predictions. Moshe Ben-Akiva, the director of MIT’s
Intelligent Transportation Systems program has helped design more
efficient toll plazas and flag unneeded on-ramps before they ever
leave the planning stage. But “our most important emphasis
is on predicting traffic and giving good alternatives,” says
Ben-Akiva, a professor of civil and environmental engineering. He
predicts that the MIT traffic simulation software, DynaMIT, will
be used to advise drivers, with radio traffic updates, phone numbers
that give traffic conditions, and computer-controlled highway signs.
These predictions are based on making sure each simulated driver
in the model has his own artificial personality - without that individuality,
the forecasts can be surprisingly wrong.
Traffic in Boston has gotten worse recently, even relative to other
American cities. Bostonian's travel time index (a measure of congestion
that takes into account typical commute distances, not just drive
time) was 11th in the nation in 1991. But by 2002, the city ranked
5th, behind Los Angeles, San Francisco, Chicago, and Washington
DC, according to the Texas Transportation Institute, which publishes
an Urban Mobility Report each year. The Institute says the average
American city dweller wastes 58 hours per year stuck in traffic.
Governments attack this problem by building roads, funding public
transit, raising or lowering speed limits, closing on-ramps during
certain hours, or metering on-ramps to only allow a certain amount
of traffic onto the freeway. But without some kind of traffic modeling,
all these efforts are essentially blind fiddling.
For longer than there have been digital computers, physicists and
engineers have labored over... |
