Raytheon's PRT 2000 (TM) Personal Rapid Transit System Project

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


The System

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


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


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.

Development History

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.

Development and Commercialization Plans

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.

Planning Issues

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)


The Potential

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


Major Characteristics

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

PRT 2000(TM) Unique Features

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

Community Benefits

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


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