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A professor of mechanical engineering sits typing at a computer keyboard,
conjuring up a scene on his monitor that looks something like the classic
computer game PacMan. White dots stream in from the right of the screen,
switch to red, and merge with green boxes, which swiftly change colour to
yellow and then red, while moving through a bewildering maze. But this is
not a video game. J. Edward Anderson of Boston University is testing an
urban transit system that he believes could revolutionise public transport
worldwide.

For the past quarter of a century, Anderson has been promoting his version
of a personal rapid transit (PRT). Other versions came and went in the 1970s,
from Europe, Japan and elsewhere in the US, but he was so convinced of the
idea’s potential that he stuck with it and, in 1983, founded the Taxi
2000 Corporation to ‘commercialise’ the initiative. Although the University
of Minnesota, Anderson’s employer until 1986, holds the patents to the technology,
he is licensed to develop it and to sub-license other developers.

Since last year, Taxi 2000 has been working closely with Raytheon, one
of the US’s top ten defence contractors, to design and build a PRT2000 system,
as they call their joint development, for the Chicago suburb of Rosemont.
Raytheon paid Taxi 2000 an undisclosed sum for its sub – licence, and guaranteed
a royalty on any PRT systems that were built as a result. Now the pair is
advising city authorities across the US and in Europe.

Anderson believes that his system benefits from the mistakes of earlier
PRT developers. ‘They went to hardware too soon,’ he notes, though none
got beyond the prototype stage. Anderson says he has also been helped by
improvements in the technology of linear induction motors and computer control
systems, two key elements of his design.

PRT2000 is ‘personal’ in the sense that it relies on small rail cars
(approximately 1.6 metres wide by 1.5 metres high by 2.75 metres long) designed
to carry up to four people who, as with a taxi, choose to ride together.
The system is ‘rapid’, not because of the speed of travel (a modest 50 kilometres
per hour, according to current plans), but rather because passengers proceed
nonstop to their destinations. Anderson says he expects fares to lie ‘somewhere
between a bus fare and a taxi fare; hopefully closer to a bus fare’.

Testing time

Soon Anderson will see his idea move out of the ethereal realm of digital
simulation and into the real world. Last October, Raytheon began building
a 1-kilometre oval test track in the grounds of one of its engineering divisions
in Marlborough, Massachusetts, and by September 1996 expects to have tried
out three prototype PRT cars on the circuit. If this project is successful,
the company plans to start building a 4-kilometre pilot system the following
year in Rosemont, near O’Hare International Airport and home to many hotels,
restaurants and convention centres. Of the urban districts in Chicago considered
for a PRT demonstration, Rosemont was selected because it had the highest
projected number of passengers – some 6000 per day.

Costs of around $40 million for the prototype system are being met
jointly by Raytheon and the Regional Transit Authority of Northeastern Illinois,
which is responsible for public transport in Chicago. The RTA became interested
in PRT in 1989. Anderson recalls: ‘We met with one guy who told another
guy, and eventually the idea made its way to the (then) chairman, Gayle
Franzen.’ Last year, after Raytheon had teamed up with Taxi 2000, the RTA
selected Raytheon as the prime contractor for the Rosemont project.

Dramatic changes

Changes in the way people live and work are making innovative transportation
concepts more appealing, according to Laura Jibben, executive director of
the RTA. ‘Traditional transit systems, which were designed to take people
from the suburbs to the city, have become increasingly ineffective as a
result of the dramatic shifts in the job market over the past 20 years.’
Two-thirds of commuters in the US now go from suburb to suburb, following
dispersed travel paths that are largely incompatible with fixed rail lines.
This means fewer people rely on public transport, and more drive their cars
to work. Only 5 per cent of American commuters use public transport, down
from 9 per cent in 1970, while 87 per cent of commuters get to work in a
car, up from 78 per cent over the same period. City authorities are desperate
to unclog their roads by luring commuters out of their cars and onto public
transport.

‘People keep telling us they would ride a system that took them directly
where they want to go,’ Jibben says. ‘They’d also like to be able to ride
alone or with friends – features that make them feel safer and more comfortable.
Well, along came a system that offered just those attributes.’ That system
was PRT2000, and the RTA liked the idea so much it agreed to spend $18
million on a prototype. In return, Raytheon has promised the authority a
royalty of 1.3 per cent on any future PRT2000 systems that it sells. Raytheon
itself is investing $20 million in the Rosemont project and seems confident
that more contracts will follow from other choked cities, in the US and
elsewhere.

Here’s how the PRT2000 system is expected to work. Sleek, driverless
PRT cars, little bigger than a family saloon, will move on wheels within
narrow U-shaped ‘guideways’, propelled and braked by linear induction motors.
(The propulsion system is described more fully in the box ‘Going out on
a LIM’.) In general, the 1-metre-wide guideways will be elevated so that
existing surface traffic doesn’t hinder the flow of PRT cars. Besides, rights
of way are also easier to obtain for elevated tracks. In places, however,
it may be more practical to install the guideway at street level, down the
centre of a highway for instance.

The system will be a single-track network, with vehicles running in
only one direction, because engineering studies have shown that the complex
interchanges required for twin tracks would make it unaffordable. A PRT2000
network will consist of numerous interconnected loops. Commuters will be
able to travel between any two points on the network, albeit by a slightly
more circuitous route than they could take if the system provided two-way
or twin tracks. Stations would be just 800 metres apart.

When they arrive at the station, passengers will buy tickets from a
machine, keying in their destination and the number of people in their
party. ‘Ideally, an empty vehicle will be waiting, ready to go; if not,
one will arrive within three minutes,’ says Raytheon engineer Brad Schupp.
A computer on board the car will read travel details from the ticket, and
will guide the car to its destination.

Unlike conventional rail-way tracks, junctions on the guideway will
not have points to direct the cars. Instead, each car’s on-board computer
will flick a switch inside the vehicle to direct it onto the right track.
‘It’s like pulling off a highway to a rest area,’ says Steve Gluck, Raytheon’s
transportation director. ‘When you need to exit from a highway, the highway
doesn’t move. You just turn the steering wheel. PRT vehicles do pretty much
the same thing.’

The arrangement means that PRT vehicles can travel close together, and
allows the system to carry as many vehicles as a crowded highway. According
to Anderson, a PRT track with vehicles travelling at 50 kilometres per
hour and spaced at one-second intervals (less than 14 metres apart) would
carry the equivalent of 4000 cars per hour, which is more than a two-lane
urban highway can manage without going into gridlock. (As a rule of thumb,
he says, a crowded but jam-free highway carries one car per lane every two
seconds; so a two-lane highway carries one car per second, or 3600 cars
per hour.)

According to Anderson, one of the biggest challenges is to prevent
the hundreds of vehicles on a PRT network from crashing into each other.
To do this, he and Raytheon have developed a control system that relies
on three kinds of computer: the computer on board each vehicle that remembers
the destination; computers near intersections to question approaching cars
about their travel plans; and a central computer to manage the entire network
by, for instance, distributing routing information from a database to
other computers, monitoring the densities of traffic at junctions and sending
empty vehicles to stations as and when they are needed.

Traffic control

Getting it right is not a trivial problem, ‘but it’s well within the
state of the art,’ says Anderson. ‘Raytheon has been developing air traffic
control software for more than twenty years. Controlling the airspace in
three dimensions is a much more difficult problem than regulating PRT, which
is basically a one-dimensional system.’

If safety is not going to derail the entire concept, what about the
economics? Anderson argues that PRT systems will be cheaper to build and
operate than conventional mass transit networks, chiefly because they are
lighter but also because the PRT vehicles run on demand, so there is less
empty running, which will help to reduce maintenance costs. He sees a PRT
system costing between one-sixth and one-third that of a tram system, for
which capital and operating costs amount to between $1 and $2 per passenger
kilometre. He notes that this makes PRT2000 cheaper than even a fleet of
city buses, which are currently the cheapest form of urban transport in
the US at around 25 cents per passenger kilometre.

Vukan Vuchic, a transport engineer from the University of Pennsylvania,
finds those figures hard to swallow. ‘They’re way too optimistic,’ he says.
‘PRT looks good on paper, but when you start deploying it, you run into
all kinds of problems. It quickly becomes very complicated – and expensive.’
In his opinion, the system combines expensive guideways with inefficient,
small-capacity vehicles. ‘You get the worst of both worlds,’ he insists.
‘In essence, what you end up with is an expensive version of the private
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There are always critics, Anderson replies. ‘Maybe it will be more
expensive than we thought, but accumulated industrial experience suggests
that costs will eventually go down.’ PRT components can be mass-produced,
which will lead to economies of scale. Further price cuts will come as manufacturers
gain experience with the new technology. ‘Take any industry,’ Anderson
says, ‘as you learn how to do things, costs almost invariably come down.’

Furthermore, PRT has certain advantages that conventional transit systems
are hard pressed to match at any price. For instance, it is well suited
to the needs of suburban areas where the population is too thinly spread
to support traditional rail systems, yet too large to rely exclusively on
the car. And, because PRT guideways are so narrow – narrower than a typical
American sidewalk – city authorities can plan and build the system without
tearing up the streets. The system is also economical in its use of space,
continues Anderson. While the average American city devotes about half of
its land to the car, in the form of highways and parking lots, for instance,
a PRT network would cover only about two per cent of urban land, he says.
‘This technology could help us reclaim part of the city. Maybe we could
convert some parking lots to parks and gardens.’ While Anderson doesn’t
expect PRT to replace cars or eliminate the need for roads, he believes
the system can restore a healthier balance between public transport and
the private car.

Cutting congestion

One benefit would be to cut traffic congestion on the roads – a growing
problem in the US and elsewhere. In the past three decades, the number
of cars per kilometre of US road has roughly doubled, while traffic delays
have tripled. Over the next three decades, says the Federal Highways Administration,
travel delays may increase fourfold, if the expected further doubling in
car use is realised.

Another of PRT’s selling points is its po-tential for bringing a district’s
geographically dispersed buildings within easy reach of one another. Rosemont
should provide a good opportunity. Chicago’s transportation officials are
counting on the PRT to tie together the assortment of hotels, restaurants
and convention centres that border O’Hare International Airport, where more
passengers come and go daily than at any other airport in the world.

A new transportation system could help to make the place more congenial,
says Charles Harris, a landscape architect at Harvard University’s graduate
school of design. He has drafted land-use and transportation plans for several
cities in the US and Mexico, and since 1991, as a consultant to Taxi 2000,
he has made several trips to Rosemont. Harris quickly realised that ‘you
can’t move around safely without a car or hotel shuttle van. It is almost
impossible to walk there, because in many cases, there are no side-walks.
Where there are sidewalks, they just end.’ He sees a PRT reducing, if not
replacing, the need for cars and shuttles.

Rosemont, however, is not the only place planning a PRT. In the US there
are SeaTac, near the Seattle-Tacoma airport in Washington state; Minneapolis-St
Paul in Minnesota, Boston, Massachusetts; Las Vegas, Nevada; Aspen, Colorado;
Fresno, California; Madison, Wisconsin. Planners in the Netherlands are
considering a PRT for Amsterdam, while their counterparts in Sweden are
doing the same for Gothenburg.

City authorities in SeaTac have already received a $750 000 grant,
mostly from the Federal Transit Administration of the US Department of Trans-portation,
to design a PRT system connecting the airport with hotels, restaurants
and car rental offices. ‘We hope to create a system that people want to
ride,’ says Roy Moore, chairman of Sky Hiways, a company in SeaTac that
was set up to develop PRT in Washington state. ‘That’s the key. In this
country so far, we have not been able to design public transit systems
attractive enough to get people out of their cars.’

The company has teamed up with Raytheon and, though con-struction will
not begin before 1996, Moore can barely wait for the system to get up and
running. ‘To reach a hotel building 2000 feet from where I work, I have
to get in my car, drive out of the lot, go through five stoplights, find
a parking space, and walk through the lot to the hotel,’ he says. ‘It can
take more than 20 minutes to travel that 2000 feet. Once the PRT is running,
I can walk out the door, step into a PRT car, and then step into the lobby
of that hotel minutes later. I won’t have to fight traffic or fight for
a parking space or fight the bad weather.’

Free hand

While PRT planners in Rosemont and SeaTac must make the system fit into
an existing urban landscape, their Dutch counterparts have a much freer
hand. Property developers planning to build a business complex for Amsterdam
on 400 hectares of farmland want a PRT system to connect the complex with
nearby Schiphol Airport. The project offers the best prospects for what
he calls ‘enlightened development’, says Harris, because the land is largely
untouched. But he is disappointed with preliminary plans that call for an
‘American-style office park’, based on the premise that most people will
drive to work. ‘They’re trying to fit PRT into a car-driven scheme, rather
than designing a PRT system with some auto access,’ he concludes.

Harris has a point, says Seth Barnhard of Barnhard Consulting in Atlanta,
who drew up the preliminary design for the PRT system proposed for the new
business complex being planned for Amsterdam. But he emphasises that this
is only the first draft. ‘You have to start somewhere. It may take forty
iterations to get it right. But ultimately, we’d like to come up with a
system in which PRT is an integral part of the design, not an add-on to
a car-dominated system. That is possible here, in contrast to other sites,
because we’re starting from scratch.’

In Minneapolis-St Paul, proponents of PRT are working to ensure that
the benefits of PRT are kept to the fore. They’ve formed a local action
group, Citizens for PRT, to campaign for the rapid transit system. ‘We want
to get this idea taken seriously,’ says Ray Warner, founder of the action
group and a former colleague of Anderson’s at the University of Minnesota.
The group is preparing a proposal to put before the state legislature that
calls for a several kilometre-long PRT line that stops, among other places,
at the Mall of America – the largest shopping centre in the US. Warner and
his fellow enthusiasts are determined to see their proposal through. ‘If
the legislature votes it down, we’ll just try again another time,’ he says.

For his part, Anderson is confident that, after 26 years of sweat and
toil, PRT will finally make the leap from drawing board to city street.
He points to history for inspiration. ‘From around 1888 to 1917, 45 000
miles of streetcar lines were built in the United States,’ he says. ‘If
that’s any indication, it’s hard to imagine how far PRT might go in the
next thirty years.’

It is somewhat ironic that streetcars began to fall out of fashion
shortly after 1917, a casualty of the ascendant car. With the world’s half
billion motor vehicles now starting to bring as many problems as benefits
– pollution and congestion being the most visible of the car’s drawbacks
– city planners are anxiously searching for alternatives. Anderson offers
a simple prescription: ‘We’re not going back to the streetcar, but forward
to a totally new transportation mode that takes available technology and
assembles it in a novel package.

Steve Nadis is a freelance journalist based in Cambridge, Massachusetts.

* * *

Going Out on a LIM

The cars of a PRT2000 system rely on linear induction motors both to
propel them round the track and to bring them to a halt at stations. A LIM
is like a standard, rotating induction motor that has been sliced open and
rolled out flat.

In a standard rotating motor, stationary coils generate a rotating
magnetic field that induces an electrical current in a conductor. The combined
action of the current and the magnetic field in which it is bathed generate
a force that causes the conductor to rotate.

In a LIM, the coils and conductor are laid out parallel to one another,
and the resulting motion is linear. Reversing the direction of the travelling
magnetic field changes the direction of the force generated by the motor.

In the PRT2000 system, the coils will be fitted in a row along the underside
of each vehicle. These electromagnets will create a moving magnetic field
that will induce currents in a flat strip of metal known as the reaction
plate, which will run along the bottom of the guideway. The vehicle can
be braked by reversing the direction of the moving magnetic field.

Raytheon has shortlisted a number of British manufacturers of LIMs to
supply motors for the pilot PRT2000 system in Chicago. Among them is Force
Engineering, based in the Midlands, for whom Eric Laithwaite is a technical
consultant. Laith-waite, former professor of heavy electrical engineering
at Imperial College, London, and now an honorary fellow, has been the leading
exponent of modern LIMs since his first paper on the subject in 1957. He
says that the technology of LIMs has not advanced significantly since the
development of a prototype tracked hovercraft in the early 1970s. The hovercraft’s
motor, which he designed, ‘accelerated the vehicle’s 23 tonnes to 108 miles
per hour against a 20 mile-per-hour headwind and stopped it again, all within
a mile’. The government shelved the project in 1974.

Force Engineering has been supplying LIMs since 1979 for sliding and
revolving doors, conveyor belts, cement factories and, most recently, the
Big Thunder Ride at the Euro Disney amusement park in Paris. ‘I’m sure there’s
a place for a PRT system,’ says Laithwaite. And what does he think has stopped
it in the past? ‘Money, as a rule.