Status Report on Raytheon's PRT 2000 Development Project (1996)
Posted with the permission of the author - Peter Samuel (pdsamuel@aol.com)
Originally published in the ITS International magazine, November, 1996, issue. Published by Route One Publishing (ITSeditor@routeonepub.com) Fax: 44 171 873 8560
Personal Rapid Transit - Raytheon's bold move
By Peter Samuel
Raytheon Corporation, best known for military and air traffic control radars,
is making a bold move into advanced transport systems. This August 23 the
first testing began of a prototype personal rapid transit system called PRT
2000, automobile-sized electric vehicles that run on an elevated guideway.The system is being developed in a partnership between Raytheon and the
Chicago-area Regional Transportation Authority (CRTA), which hopes to build a
system 1998-2000 if the new test track and prototypes perform to
expectations. The test track is located on the grounds of a Raytheon
engineering facility at Marlborough Massachusetts on the outskirts of the
Boston area, and consists of a elevated guideway loop 650m long, and one
station. Three cars are being built for the test track. 75 Raytheon
engineers and technicians are working on the project, about half software
writers.In the first test car number one went backwards on a forward command, ITS
magazine has been told, a malfunction that was quickly traced to a miswired
motor, and easily corrected. But it was a mistake that could have been
embarrassing if TV cameras had been humming and photographers present!Raytheon is not looking for publicity until about the middle of 1997 when it
hopes to have worked any problems out of the system, and to be running three
cars at speed.Stephen J. Gluck, Raytheon's Manager for Surface Transportation told us he
is pleased with the system's performance so far though it is early in the
testing. In the first phase, to last the remainder of 1996, the company will
test the operation of the single car on the track, what he calls "rudimentary
functioning." "We are looking at the quality of ride, the precision of stops, smoothness
of acceleration, noise, speed control, brakes. There haven't been any real
surprises so far. The guideway went up very nicely indeed in almost exactly a
year and we got it right first time. No need for any adjustments there. So
far the only thing we have to redo is the electrical grounding, no big deal."Gluck said the engineers still have to specify the algorithms for electronic
synchronization of the two electric motors used in each car: "We knew we'd
have to fine tune the electronic coupling that is needed to ensure that the
two motors are working together and not dragging on one another. We're doing
that at the moment."Early 1997 when the testing crew bring the second and third cars onto the
track a second phase of tests will begin in which the interaction of cars
will be demonstrated. Gluck says the company's expertise in air traffic
control has given it an important start in developing the algorithms for PRT.Developing a system to manage lots of PRT cars on a guideway network has a
lot in common with handling the maintenance of safe spaces between aircraft
flying in crowded airspace.
And despite its image as a military equipment company Raytheon has extensive
non-military products. It pioneered the microwave oven in the 1950s, a
spinoff of radar, and makes a range of home appliances in the US under the
Amana brandname. And it owns a large construction company Engineers and
Constructors Inc. which built the PRT guideway.By the end of September 1997, unless some unexpected problem is revealed,
Raytheon should have tested all the major components of the PRT 2000 system.
Different stations will be simulated by different number of pass-bys of the
test station and merge/diverge trials. Raytheon has built the guideway
with a variety of grades and turns including one section with a slope of 10%
to test traction, and will test for the ability to cope with ice and snow
this winter. The test track has been has built with different guideway spans,
between 27.4m and 36.6m, in order to test the maximum span it can specify
without excess vibration.Personal rapid transit is distinguished from other forms of automated
guideway transit or peoplemover systems such as VAL, Skytrain and the
Docklands Light Rail by two characteristics (1) vehicles are sized like
taxicabs for personal use by an individual or a group such as a family (2) it
provides a non-stop ride from origin to destination having by-passable or
off-line stations.Attempting to combine the attributes of the automobile with the electric
propulsion and safe guideway of transit, PRT is an idea that has been
proposed, modeled, designed and prototyped for over thirty years, but never
implemented anywhere for regular service. A system named "Personal Rapid
Transit" built with federal funding by Boeing Company in the 1970s operates in
the university campus town of Morgantown, West Virginia to this day. That
system is a PRT in so far as all the stations are off-line allowing non-stop
origin-to-destination travel, but the vehicles are larger than true PRT, the
size of small buses and hold up to 20 passengers. True PRT is defined as cars
with a maximum of 3 or 4 passengers.Raytheon's design uses cars 3.96m long by 1.83m wide and 1.65m high on a
wheelbase of 2.54m weighing just over 2 tons empty. Powered by a pair of 50KW
AC motors that will accelerate them to 48km/hr the motors also provide
regenerative braking, though discs are available for emergencies and parking.Chrysler automotive axle, suspension and run-flat tires are used. The
vehicles seat four people (2 in fold-down jumpseats to allow space for a
wheelchair to enter and turn.) The cars run in a 1.83m wide steel U-shaped
track on concealed high pressure pneumatic tires. The track is supported on a
910mm diameter tube beam on similar sized steel columns.
Small unmanned stations will present travelers with a map of the system,
and having selected the destination each passenger will pay by cash or
magstripe card. A magstripe ticket will be taken by the traveler to the
first available car, where a reader nearby will transfer the encoded
destination to an in-car computer, allowing it to travel non-stop by the most
direct route to the selected destination. The Raytheon guideway has no moving
parts and switching is accomplished at discontinuities in control rails by
means sideways movement of directional control wheels in the chassis of the
vehicle.
Cars will be parked at the stations and, when empty, moved
automatically around the network to stations with a deficit of waiting cars
from stations with a surplus - to improve the odds of passengers finding cars
waiting for them when they arrive at stations.In such a small-vehicle system passenger carrying capacity is critically
governed by separation between vehicles or what is called "headway" in the
PRT community (the minimum time needed after a vehicle has passed a point in
the system before the next vehicle can pass.)Raytheon is building a system to a 2.5 second headway which gives a maximum
capacity of 1,440 cars/hour. A Raytheon table shows that this provides a
passenger capacity of 1,730/hour assuming average 2 passengers/vehicle and
60% effectiveness (40% of cars being lost to deadheading or empty vehicles
relocating themselves to stations short of cars). But the company hopes to
improve headway eventually to one second, boosting carrying capacity 150%, at
which level it is a higher volume system than light rail, though well short
of heavy rail transit.
Headway is limited by the switch maneuvers - the handling of cars moving
toward converge points at the same time, slowing one to give priority to the
other. PRT with its many stations, all off-line, and its looped-grid layout
of one way track is probably the most switch-intensive transport system yet
conceived. The system has to handle repeated close encounters at switches
requiring enormous reliability in sensing, computing, braking, and other
controls, PRT experts say.Raytheon will test and refine the system for about a year, and then - late
1997 - its co-sponsor, the Chicago Regional Transportation Authority (CRTA)
will decide whether to deploy. CRTA has a PRT layout designed for a
conference center and hotel complex at Rosemont near the Chicago O'Hare
airport. A 5km triple looping layout with about 8 stations and 40 cars would
feed passengers to the CRTA's Blue Line rail transit station.The CRTA is sharing the $40m cost of the Marlborough test track and
prototype vehicles with Raytheon, and is entitled to a 1.3% commission on any
further sales by Raytheon. Preliminary designs for the PRT 2000 have been
done for Boston's Logan Airport, SeaTac City near the airport of Seattle
Washington, and the central business area of Gothenburg, Sweden. A study is
under way on applying the Raytheon PRT in Providence, Rhode Island.Raytheon started by buying rights to designs of a long time PRT designer J.
Edward Anderson, a professor of mechanical engineering at the University of
Minnesota. Anderson's original design was smaller and lighter than
Raytheon's PRT-2000. He envisaged single bench seat cars of about 700kg
accommodating a maximum of 3 persons on a much smaller track, but the CRTA
says the need to provide full wheelchair space was one factor forcing the
increased size. Anderson wanted linear induction propulsion in place of the
regular electric motors and traction tires.
PRT has the support of a small number of very bright U.S. engineers and
other transport specialists, who say that mass public transit with its large
vehicles and many station stops is a hopeless loser in the dispersed
decentralized suburbs of modern America. And they say that in the present
political climate it has to be able to be financially self-supporting, unlike
buses and rail. Raytheon and CRTA have embraced that idea and hope to produce
a system costing around $14 million/km to build. Even more important they say
it has to offer a high standard of individual service at very low operating cost.For more details, contact Blanche Necessary at Raytheon; fax 703 416 5916 or at the Chicago RTA; fax 312 917 1344. Raytheon also has a PRT 2000 Web site . (no longer valid)
Last modified: February 16, 2008
