By Jeffrey Winters
The maze of cobalt-blue steel rails, which extends across a
parking lot and
into the surrounding woods at a Raytheon test site in Marlborough,
Massachusetts, looks like a roller coaster for the faint of
heart. Three rubber-
tired vehicles with room for four passengers each move quietly
along a
2,000-foot-long circuit of elevated tracks. There are no thrilling
drops, crazy
loops, or screaming joyriders. But as the vehicles change tracks
independently
in response to commands from a remote computer, visitors get
a glimpse of a
revolutionary means of transportation that Raytheon engineers
hope will entice
twenty- first-century suburb-dwellers to leave their cars at
home: personal
rapid transit.
The typical American suburbanite these days would be helpless
without an
automobile. With rare exceptions, even folks who commute to
work by train
or bus tend to drive everywhere else. Since 1950, the percentage
of
Americans living in suburbs has more than doubled, from 23 to
50 percent.
And in the last three decades the number of cars and trucks
on the road has
grown six times faster than the human population. That means
suburbanites
are spending a lot of precious time stuck in traffic jams, and
not just during
rush hours. Also, the nearly one-third of all Americans who
can't drive
because of age or disability intensifies the need for public
transportation. Their
ranks will swell as the baby-boom generation grows old and gray.
A few
years down the road, public transportation—now an anomaly in
the
suburbs—will become a necessity. The good news: Prototypes are
in the
works for systems that could make it a lot easier for busy suburbanites
to get
where they want, when they want, with few hassles.
The concept behind the
Raytheon PRT 2000 system
marks a radical break with
conventional notions of mass
transit. Small rail stations would
be spaced about a third of a mile
apart, a short walk from any
point in the network. An
escalator would whisk the rider
up to the elevated platform,
where a vending machine would
sell tickets to specific
destinations. If a vehicle isn't
already waiting at the station, a
central computer would dispatch
a single car to pick up the
passenger and as many as three
companions. Once loaded, the
car would zip along above traffic
on a six-foot- wide guideway
running 16 feet above the street,
directly to the station the rider
had requested.
The system would be the next best thing to robot-driven taxis.
A passenger
would not have to follow fixed schedules or ride with strangers.
"And unlike
linear systems, it requires no transfers," says Raytheon engineer
Steven Gluck.
"Any car can take you anywhere within the system."
Advanced computerized dispatching is the hallmark of the PRT
2000. In the
1980s, Miami and Detroit built so-called "peoplemovers," which
feature
driverless rail cars that carry a few dozen passengers at a
time along elevated
tracks. But the cars are programmed to stop at every station,
regardless of
whether there's anyone to pick up or drop off. This slows them
to a crawl:
cars in the Detroit system average a mere 12 miles an hour.
By contrast, PRT
2000 dispatch computers would calculate the route an individual
car should
take and relay that information instantaneously to the car.
Meanwhile, the
processor in the car would monitor the distance from any car
ahead. Unlike
peoplemover systems, the Raytheon model has stations set up
as sidings off
the main track, so when one car stops to let off passengers,
others can zip
past. And because the system is a network of linked loops, it
would be easy
to expand by simply adding more loops.
Raytheon and the Northeastern Illinois Regional Transportation
Authority
have already spent more than $50 million to test PRT 2000 and,
if additional
funding is approved, the first operational system could be erected
three years
from now in Rosemont, a suburb of Chicago. The three-mile network
will
connect several hotels with a convention center and a rail station,
vaulting
passengers over expressways and acres of bleak asphalt.
Personal rapid transit is designed for short-hop trips in the
suburbs, but longer
journeys pose different problems. As new houses—and new
workplaces—are built farther and farther from the centers of
large cities, the
automobile commute has become increasingly difficult. Commuter
buses and
light rail are often painfully slow and inconvenient. Last year
Congress
allocated $30 million to the Federal Transit Authority (FTA)
for feasibility
studies of a new rail system that could whisk passengers between
far-flung
suburbs or the outer suburban fringe to the heart of a city
in minutes.
Magnetically levitated vehicles, fondly known to their boosters
as maglevs,
would travel either along aboveground tracks or through underground
tunnels
at astonishing velocities. Maglevs tested in Germany and Japan
have been
clocked at speeds exceeding 300 miles per hour.
Until now, the biggest obstacle to maglevs has been cost. German
and
Japanese prototypes use superconducting electromagnets that
operate at
subfreezing temperatures, entailing enormous refrigeration expenses.
"The cost
of light rail is $15 million a mile," says FTA engineer Edward
Thomas. "If
maglev is $145 million a mile, it's out of our reach. But if
we can get the cost
of maglev systems down to, say, $20 million a mile, and it outperforms
light
rail, then it could be cost-effective."
Inductrack, a new maglev system developed by the Lawrence Livermore
National Laboratory, could be the answer. Inductrack relies
on a set of
conventional magnets mounted on the underside of a train and
arranged in
such a way that most of the magnetic force is placed on one
side. That
effectively doubles the power of the magnets. Small closed coils
of insulated
wire are embedded under the track to provide levitation. As
the magnets pass
over the tracks, their field induces an oppositely aligned field
in the coils. The
two fields then repel, pushing the train off the ground, while
a separate set of
magnets accelerates and decelerates the train.
Tests last year on small Inductrack carts showed promise, although
the train is
unlikely to approach speeds of 300 miles per hour. But speeds
of just 80
miles per hour would result in quick and cost-effective suburb-to-suburb
public transportation.
Another idea that has yet to reach the prototype stage would
give
suburbanites even more travel options than personal rapid transit
or maglevs.
Palle Jensen, a Danish inventor, hopes to combine the flexibility
of the
automobile with the high capacity, efficiency, and safety of
rail in a system he
calls Rapid Urban Flexible transportation. Jensen envisions
a fleet of small
electric cars that can operate in ordinary traffic as well as
in linked trains on
elevated monorails. The cars would ride astride beams, drawing
electricity
and central control from them. Because the longest part of any
journey would
be on the beam, the system extends the effective range for electric
vehicles.
Passengers would be spared the aggravation and safety hazards
of highway
traffic for most of their trip.
With elevated rail tracks crisscrossing the landscape, the suburbs
of the future
may begin to resemble something out of an episode of Flash Gordon—Peril
from the Planet Mongo. But the alternative is unthinkable: driving
in
bumper-to-bumper traffic, amidst a cacophonous symphony of car
horns, just
to get to the nearest grocery store or shopping mall. Even Gordon's
arch
nemesis, Ming the Merciless, would be hard-pressed to come up
with a more
excruciating torture.
RELATED WEB SITES:
Innovative
transportation Technologies
PRT 2000
RUF homepage from Palle Jensen
Office of
Research, Demonstration and Innovation from the Federal Transit
Administration
SkyTran, another personal
transit system
© Copyright 1999 The Walt Disney Company.