Richard Tauber and Angelo Fergione(1)
Advances in technology now make possible the
realization of a dream many planners have had of a
new form of urban transportation that can reverse the
trend of ever increasing congestion and pollution that
has led to the strangulation of metropolitan regions all
over the world. The new system PRT 2000(TM)
which is a new-generation Personal Rapid Transit
(PRT) system is a synthesis of the work of hundreds
of inventors engineers and planners and is ready for
construction of a demonstration. Several rounds of
engineering cost analysis indicate that in many
applications PRT 2000(TM) can be built and operated
at a cost lower than existing transit modes.
Concept definition efforts in Personal Rapid Transit
(PRT) during the past twenty years have set the stage
for its development and commercialization. To realize
the full potential of this technology the system concept
needs to be carefully implemented and its applications
carefully chosen so that they are practical
commercially viable and accepted by the public. !n
order for a public transit system to be commercially
viable the transit system patrons must find the system
convenient and its level of service acceptable. The
paper provides a histories! introduction a rationale for
the features of the system a discussion of planning
issues and some implications of the system.
The July 1969 issue of Scientific American carried a
lead article "Systems Analysis of Urban
Transportation." (1) It was a summary of a federally-
funded study aimed at seeking new solutions to
problems of urban transportation. The study
performed by an interdisciplinary team of specialists
at the General Research Corporation concluded that"
. . . even with the most optimistic view of what might
be achieved through improvement of the existing
methods of transportation such improvements could
not satisfy the tea[ needs of our cities in terms of
service . . . "and that" . . . in certain circumstances
installing novel personal transit systems may already
be more economic than building conventional
systems such as subways."
Comparison of the current situation with the 1969
Scientific American article shows that those authors
were right. The problems of congestion discussed are
not only unresolved today they are much worse (3).
By the mid-1970s however the optimism of 1969 that
new solutions were just around the corner faded.
During the 1970s many new personal transit solutions
were invented and promoted but many more people
looked to the promise of huge federal grants to build
conventional systems and new automated systems
that used conventional service concepts. The
conventional transit lobby was strong while the lobby
for new personal transit systems was weak. The
promoters of new automated systems were too
optimistic. They lacked the underlying theory and
practice needed to design them correctly and certain
needed technologies were not ready.
However thorough system planning which evolved
over the past 25 years combined with modern
technology make it possible to do better now. The
process began in the early 1970s. Dr. J. Edward
Anderson (4) coordinated an interdisciplinary team of
15 faculty members at the University of Minnesota
aimed at understanding the needs in enough detail to
plan and specify a new transit system that could
satisfy a complex set of service performance
environments[ sod economic requirements. The team
got involved with the local transit-planning process.
They studied and debated a wide range of related
issues and began their own technical analysis of the
new personal transit systems. This led to planning
and conducting conferences - three of them called the
international Conferences on Personal Rapid Transit
(PRT) .(4) The team accepted the 1969 judgment that
the promise of the future would lie in these new PRT
systems and they wanted to improve on them.
As chairman of these conferences Dr. Anderson was
privileged to visit virtually all of the work on new
transit systems in the world. Through a variety of
funding sources he and his colleagues were able to
sustain a steady advance of technical and planning
work through the l970s. As a result of site planning in
Indianapolis in 1979-81 in which existing PRT and
other automated transit concepts were included it
became clear that a new design should be developed.
That new design called Taxi 2000 was initiated in
1981 and was licensed to Raytheon Company in
1993. it will be commercialized under the name PRT
2000
PRT 2000(TM) grew out of over a decade of
systematic analysis of the problems of contemporary
urban transportation involvement in a variety of transit
planning studies study of characteristics of new
systems required to solve these problems study of
how these systems might fan and how to make the
design fault tolerant and fail safe study of over 46
categories of tradeoffs or design choices development
of long lists of design criteria and engineering analysis
of each tradeoff to determine the best choice. The
requirement for cost-effectiveness--to so reduce costs
and increase service that the system could be built
and operated at a profit - was a primary goal. By
applying this process the essential features of this
PRT system are derived much as one derives a
mathematical formula from a form of the equation for
cost per passenger-mile of a transit system suitable
for systems analysis (5).
A brief summary of key features is as follows: An
exclusive guide way is required to safety attain high
average speeds and must be small to minimize cost
and obtrusiveness. The cost of the fleet regardless of
vehicle size is minimized if the average trip time is
minimized. The average speed is maximized if all
intermediate stops are eliminated - possible if all stops
are on bypass tracks off the main line and practical if
the smallest size vehicles are used. Fortunately
dynamic structural analysis shows that the weight of
the guide way is reduced to a much lower value than
might be expected if the smallest size vehicles are
used. To minimize cost the vehicles have to be smart
enough so that they can be used by small parties of
people (6) traveling together by choice.
The nonstop trip is made possible by use of off-fine
stations. Ridership is maximized if these stations are
closely spaced in a network of interconnected guide
ways that eliminate the need for passengers to
transfer from line to line. This feature requires safe
reliable rapid switching realized by 1) use of a new in-
vehicle switch having no moving track parts 2)
automatic control 3) appropriate switching logic and 4)
electronic communication. Additionally a new and
comprehensive method of determining the reliability
required of all subsystems which quantified the
advantages of redundancy and failure monitoring
gave confidence that a very reliable system could be
built if certain design choices were made.(7)
Analysis of operating and maintenance costs per
passenger-km showed that these costs are minimized
if operation is strictly on demand and if empty vehicles
are rerouted by a central computer from stations with
excess vehicles to stations with shortages. To
minimize costs vehicles must wait at each off-line
station for passenger or freight moving only if travel is
required. This is unlike conventional bus and rail
transit in which vehicles must move on a schedule
independent of fluctuations in passenger demand
thus forcing passengers to wait for vehicles. This is
the concept of PRT as envisioned decades ago (9),
now derived by minimizing each factor in the cost per
passenger-km.
During the 1970s experimental programs in the
United States England France Germany and Japan
demonstrated almost every reasonable way of
implementing the PRT concept and many papers on
the technology economics and planning of these
systems were written (8). PRT 2000(TM) was designed
by building on this work. Much of its theoretical
foundation is described in Dr. Anderson s textbook
(9).
To permit operation at the closest practical headways
PRT 2000(TM) uses a combination of electric motor
propulsion and microprocessor control not available a
decade ago in the small size and low weight required.
Such features provide high capacity safely and
reliably with minimum noise and air pollution. it uses a
unique guide way configuration that meets criteria
obtained by analyzing and planning these systems.
PRT2000(TM)is built of available technology
proven during the past two decades in industrial
military and automated transit applications.
The steel guide ways of PRT 2000(TM) are lightweight.
To increase the natural frequency in bending and
torsion they are rigidly bolted to support posts.
Expansion joints are included and stiff steel running
surfaces are overlapped and adjusted to provide a
smooth ride. Guide way covers aid winter operation
reduce lateral air drag and permit the color and
texture of the external surface to complement the
cityscape. The elevated configuration reduces the
land devoted to transit to that needed for posts and
stations. PRT 2000(TM)is easy to erect easy to
expand and easy to move. The electric motors and
pneumatic tires running on steel rails all but eliminate
the air pollution noise and vibration associated with
conventional transport.
At each station a map of the system of lines and
stations is posted near a ticket machine similar to a
bank cash machine. A patron selects a destination on
the network whereupon a display verifies the
destination and indicates the fare which may be paid
by cash a prepaid card or a credit card. The machine
then dispenses a ticket on which the destination is
magnetically encoded. The patron takes the ticket to
the loading platform and inserts it into a slot in a
stanchion in front of the first empty vehicle in a line of
usually three or four vehicles like a sheltered taxi
stand. The ticket is read and the destination is
transferred to a computer aboard the vehicle. The
door then opens the patron or a group of two to four
patrons traveling together enter sit down and the door
is closed. This action informs the vehicle
microprocessor that the vehicle is ready to go. A
wayside computer senses an opening the vehicle
accelerates and merges into the stream of traffic that
is by-passing the station and proceeds nonstop to the
planned destination.
The result of system optimization for minimum life-
cycle cost is a breakthrough. Detailed cost estimates
repeated in successive stages over a period of six
years show that in many reasonable applications PRT
2000(TM) can be built and operated at far lower cost
than existing rail transit modes. The result is also
energy minimization - the combination of nonstop
travel and lightweight streamlined vehicles
substantially increases energy efficiency.
The remarkable result of cost minimization is a
humanizing technology. PRT 2000(TM) requires vehicles
to wait for people rather than people to wait for
vehicles. it provides a short predictable nonstop trip
on a network of guide ways a seat for everyone
climate control no transfers minimum or no wait 24
hour on-demand service ease of use privacy no
crowding space for luggage no jerky motion no
objectionable sounds no smelly fumes minimum
anxiety maximum safety minimum land use and
minimum disruption to businesses and the community
while the system is installed. PRT requires no
turnstiles which are barriers to the handicapped and
provides mobility for all including those who are
unable to drive. The system can also carry mail
groceries luggage household goods appliances
furniture and other materials.
The appearance of PRT 2000(TM) is unobtrusive. As
compared to other transit modes little space is
needed for guide ways. As surface traffic is reduced
existing streets can be partly turned into linear parks
and gardens bringing to the city a balance with nature
enticing to all. PRT 2000(TM) does for horizontal
development what the elevator did for vertical
development. Study of factors that induce people to
ride transit suggest that disappointing ridership on
present people movers using conventional transit
service concepts bears no relationship to the potential
ridership on a PRT 2000(TM) system.
After 13 years of PRT study the design of what
became PRT 2000(TM) began in three quarters of
Senior Mechanical Engineering Design classes during
the academic year 1981-82 and continued under a
patent-development grant from the University of
Minnesota followed by private investment funds. With
the help of University of Minnesota administrators a
company (10) partly owned by the University was
formed in June 1983 to develop the new system.
In April 1984 an agreement was reached with Davy
McKee Corporations Chicago Technical Center which
intensified the development effort by developing bid
packages and refining cost estimates on all
subsystems. About 150 separate pieces of analysis
were completed to quantify the component
specifications. Computer simulations were developed
to analyze and synthesize the guide way configuration
the vehicle propulsion and control system station
operations and to determine all forces and defections
in passing through the critical branch sections of the
guide way under extreme loading conditions.
In 1986 circumstances caused the effort to shift to
Boston where in 1987 executives and engineers at
Raytheon and other organizations became interested
assisted with applications studies and caused a
thorough review of the design to be undertaken.
The result was that the planned development program
time schedule and cost were corroborated. Credibility
of the design a fundamental element in overcoming
the deficiencies of the past was further increased
through a study performed in 1988 by the Advanced
Transit Association, (11) and through the efforts of its
Chairman Thomas H. Floyd Jr. (12).
These efforts combined to make possible a
successful bid to perform a one year $1.5M study of
PRT for the Northeastern Illinois Regional
Transportation Authority. The study managed by
Stone & Webster Engineering Corporation was
completed in the spring of 1992.1t found that
development of the system is straightforward and the
costs and schedules produced previously were
reasonable. Four Chicago suburbs (Deer field Lisle
Rosemont and Schaumburg) became candidates for
the first demonstration and in April 1993 Rosemont
was selected. On June 3 1993 the RTA Board voted
to proceed with hardware development under the
leadership of Raytheon Company. The contract was
signed on October 1 1993.
The hardware development program will prove the
performance of PRT 2000(TM) on an oval track with
one off-line station and three prototype vehicles at
Raytheon s Electronic Systems Division facility in
Marlborough Massachusetts USA. The prototype test
program is expected to begin in 1996 following which
the Rosemont demonstration is planned. Additional
deployments in the United States and abroad are
being considered in parallel.
The layout of PRT networks is a multi-step process
involving a number of issues. For layout of a PRT
network human comfort criteria impose limitations on:
1) the length of off-line guide ways 2) the minimum
superelevated-curve radius and 3) the minimum
distance between guide way branch points. These
considerations illustrate the ways in which the
selection of line speed enters the planners thinking.
The system may be placed underground at grade or
above ground in which case a clearance requirement
of sin is the standard bridge clearance in the United
States. Aver consideration of these choices most
planners choose to elevate the system. PRT 2000(TM)
particularly lends itself to elevation because of the
small cross section and the use of covers that can be
textured and colored to suit the cityscape through
which it passes. The system is designed for post
spacing in the range from 27 to 37m. This distance
can be varied by small amounts to avoid underground
utilities or by larger amounts to span freeways rivers
etc. The fully loaded guide way is sufficiently smart
and lightweight to be easily supported from the sides
of buildings or run through buildings. in a downtown
area we envision that the stations will typically be
integrated into buildings. With a standard propulsion
system grades can be as steep as 10 percent.
Once a system is laid out based on these
considerations and with knowledge of the travel
patterns it is necessary to perform a detailed site
specific ridership analysis. Standard ridership models
are calibrated based on existing transit systems and
base the estimate on relative time and cost. Until
experience is obtained there is no solid basis
established in these models for taking into account
the superior service offered by PRT. Even with these
limitations the above-mentioned Indianapolis study 3
produced about 4,000,000 passenger-km per year per
lane-km on a network PRT system ample for
profitability with reasonable fares. Because of limited
ability to predict ridership prior to actual experience it
is best to expand PRT systems cautiously. Having
estimated the ridership the peak-period line and
station flows are calculated to determine potential
bottlenecks. This should first be done analytically and
then simulated on a computer to study short-term
fluctuations. A computer program designed to
calculate and display lines and stations including a
ridership program and a cost program permits the line
and station locations to be varied to optimize the
system. This can be done with confidence after the
ridership model is calibrated based on PRT 2000(TM)
characteristics.
The above are only the direct factors involved in
laying out and optimizing a given PRT 2000(TM) system.
Having completed the analysis the planner and urban
designer can consider broader issues related to the
kind of community made possible by deployment of
PRT2000(TM)
lntermodal complement to all transportation systems
Small private vehicles seating up to 4
On-demand 24 hour service
Non-stop origin-to-destination
Automated Guideway Transit (AGT) - dedicated right-of way
Exceptional personal security and safety
Affordable (Capital/Operations/Maintenance)
Short headways, high throughput
All weather operation
Environmentally benign, aesthetically pleasing
Easily installed
Quiet efficient electric propulsion
Decreased congestion
Improved regional accessibility
Minimization if not elimination of transit subsidies
Increased potential for horizontal development
More efficient use of parking facilities
More efficient movement of people and goods
Lower levels of air and noise pollution
Rapid inside-to-inside transportation
The 24-hour community
Freedom of movement for physically challenged children and elderly
Faster accessibility to stores, clinics and schools
Lower street-repair costs
Fewer and shorter street disruptions
1. Mr. Tauber and Mr. Fergione are with the Raytheon
Company Electronic Systems Division Marborough
MA USA.
2. William F. Hamilton and Dana K. Nance Systems
Analysis of Urban Transportation, Scientific American
221 (1969):19-27
3. Frederick Rose Despite Huge Outlays Transit
Systems Fail To Lure Back Riders, Wall Street Journal
June 29 1993 page 1.
4. Dr. Anderson is the CEO of the Taxi 2000
Corporation, Minneapolis, MN USA .
5. Personal Rapid Transit { (Minneapolis: Audio-
Visual Library Services University of Minnesota 1972
1974 and 1976 respectively)
6. J: E. Anderson, Optimization of Transit-System
Characteristics, Journal of Advanced Transportation
18 (1984):77-111
7. J. E. Anderson, Automated
Transit Vehicle Size Considerations, Journal of Advanced Transportation , 20(1986):97-105.
8. J. E. Anderson, Transit Systems Theory (Lexington
MA: D. C. Heath Company, 1978).
9. Donn Fichter, Individualized Automatic Transit and the City (Chicago: B. H. Slikes, 1430 East 60th Place
Chicago IL. 60637, 1964).
10. For a list of references see J. E. Anderson, R. D.
Doyle and R. A. , Personal Rapid Transit, Environment 22(1980):25-37.
11. Transit Systems Theory, op.cit.
12. The original name of the company was Automated
Transportation Systems lnc. In 1986 it was changed
to the Taxi 2000 Corporation.
13. Advanced Transit Association, Personal Rapid
Transit, Journal of Advanced Transportation ,1989.
14. Thomas H. Floyd, Jr., Personalizing Public
Transportation, The Futurist, Nov-Dec,1990.
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Last modified: April 24, 1996