Ultralight Rail and Energy Use Ultralight Rail and Energy Use

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Ultralight Rail and Energy Use

Dr. John A. Dearien

CyberTran International, Inc.

As Published In: Encyclopedia of Energy, Elsevier Publishing, Cutler J. Cleveland,EditorIn-Chief, March 2004.

I. IntroductionII. Definition of Ultralight RailIII. A Brief Discussion of Conventional RailIV. Capacity and Energy Consumption of Highways

V. Ultralight Rail - Operational CharacteristicsVI. Energy Requirements of Ultralight Rail and Conventional RailVII. Energy Saving Opportunities with Ultralight RailVIII. Bibliography

GLOSSARY

Guideway The rail, support structure, powerdelivery conductors, and control sensors thatmake up the path on which ultralight vehiclesmove.CONSIST An individual unit or multiplevehicles traveling in a linked setHEADWAY The time period between trainsor individual vehicles passing a particular pointon the guideway.GRADE The slope, or inclination, of theguidewayPPHPD (Passengers per hour per direction)The measure of capacity of a rail transitsystem, in terms of the maximum number ofpassengers the system can move in one

direction.kWhr (Kilowatt hour) Base energy unit 1kilowatt of power used for one hour

I. INTRODUCTIONIn order to best describe the relationship

between ultralight rail and energy, it is

necessary to establish a basis of understanding.This basis is best defined in terms of the energyrequirements of known and familiar modes oftransportation, since there are so few examplesof ultralight rail in operation at the moment.

This article establishes this basis in terms ofconventional rail systems, and where applicable,bus, automobile and truck systems. The readeris taken through the basic characteristics of bothconventional and ultralight rail systems,followed by a comparison of the two systems,with an emphasis on the energy aspects of theirdirect operation. The energy aspects ofultralight rail in the overall transportationsystem of the United States is analyzed anddiscussed.

II. DEFINITION OF ULTRALIGHTRAIL

Ultralight rail (ULR) is at the low end of thespectra of weights of rail vehicles, generallyconsidered as any vehicle with a loaded weightless than 10,000 pounds and with a more


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personal type of operation (Irving, 1978). Thiscompares with Light Rail Transit (LRT,www.travelportland.com/visitors/transportation.html ) vehicles that can weigh over 100,000pounds loaded and the locomotives that pull

freight, commuter, and Amtrak trains andweigh over 300,000 pounds. The weight of apassenger vehicle on what is classified as aHeavy Metro Rail, like BART in the SanFrancisco Bay area (www.bart.gov ), the NewYork City subway, etc., can actually weigh less(around 60,000 pounds) than an LRT vehicledue to its construction and propulsion system(Light referring more to total passengercapacity than individual vehicle weight).

Figure 1 CyberTran Vehicle on Test Track

in Alameda, California

In the ultralight range of steel wheeledrail vehicles, there are several technologies indevelopment but none in operation. CyberTran(www.cybertran.com), shown in Figure 1, is anexample at the top of the range (10,000 pounds,loaded) and an Australian technology,Austrans (www.Austrans.com ), is somewhat

lighter at approximately 6600 pounds, loaded.Futrex (www.futrexinc.com) is between theultralight range and the LRT, or full size railvehicles, weighing approximately 20,000pounds loaded.

There are several systems with vehiclesin the ultralight category that utilize rubbertired vehicles and channel type guideways,

such as TAXI 2000 (www.taxi2000.com ) andthe ULTra system (www.atsltd.co.uk) at theUniversity of Bristol in Cardiff, England. TheMorgantown People Mover(www.wvu.edu/~facserv/prt.htm ), shown in

Figure 2 Morgantown People Mover Vehicle

Figure 2 at the University of West Virginia,Morgantown, WV is just over the 10,000 poundloaded weight (9000 pounds empty with apassenger capacity of 21), but represents thebest operating example of ultralight typesystems. While these rubber-tired systems sharemany of the energy saving aspects of ultralight

rail, they have a larger rolling friction than steelwheel on steel rail. The reader should keepthese systems in mind regarding energydiscussions that are functions of size, passengerload, small infrastructure costs due to vehiclesize, and vehicle movement options generatedby small vehicles. An excellent coverage ofultralight systems and innovative transportationconcepts under development can be reviewed atthe website of Professor Jerry Schneider,University of Washington.

(http://faculty.washington.edu/jbs/itrans)

III. A BRIEF DISCUSSION OF

CONVENTIONAL RAIL

Regardless of the weight of the vehicle ultralight to heavy metro - a steel wheel on asteel rail is the most energy efficient way to


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move a load over land. This efficient processwas initiated by placing a iron rimmed wagonwheel on a iron plated beam, allowing draftanimals to pull much heavier wagon loads.With the advent of steam engines to pull the

wagons and flanges to keep the wagon wheelsfrom slipping off the rails, the essence of themodern railway was born in the early 1800s inthe coal mines of England, and quickly spreadover the rest of the world. The energyefficiency of the basic steel wheel on steel railsystem was further enhanced with the advent ofroller bearings on the axles and propulsionsystems with electric and diesel-electric powerplants.

A. Energy Efficiency of Steel Wheel on SteelRail

The primary reason for the energyefficiency of steel wheel on steel rail vehiclesis the extremely low rolling resistance of thewheel, even under very high loads and/orstresses. A typical loaded freight car canweigh as much as 280,000 pounds, beingsupported by 8 wheels, with each wheelsupporting over 35,000 pounds. This wheelload is supported through a contact patchapproximately the size of a dime, resulting in acontact stress between the wheel and the rail ofaround 100,000 pounds per square inch (psi).While this stress actually deforms the steelwheel and the steel rail, the energy lost in thisprocess is small compared to the energy it takesto deform and roll a rubber tire under heavyload. The force required to roll a standardrailroad vehicle on level ground isapproximately 2 4 pounds per ton of vehicleweight. (Armstrong, 1994)

B. Conventional Systems - Vehicle Weights

and Capacities

Conventional transit vehicles typicallyweigh much less than loaded freight cars, butstill represent a heavy load to place on wheelsand rails. A BART car weighing 80,000pounds loaded, and supported by 8 wheels, has

a per wheel load of 10,000 pounds. ArticulatedLRT vehicles generally have 3 sets of 4 wheeltrucks, and with loaded weights up to 120,000pounds, results in a load of 10,000 pounds perwheel. These vehicles roll even more efficiently

than heavily loaded freight cars, but stillrepresent a sizable load, with energy absorbingdeformation of the wheel/rail contact area.Rolling friction of typical transit vehicles are onthe order of 3 pounds per ton. Figure 3 shows atypical LRT vehicle, operating at ground levelin Portland, Oregon.

Figure 3 LRT Vehicle in Portland, Oregon

Figure 4 shows an example of a HeavyMetro Rail system, BART, operating onelevated track in the San Francisco Bay area.LRT vehicles can transport over 100 passengersper vehicle and a 10 car BART train can carryover 1000.

Figure 4 BART Train on Elevated Track


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C, Operation of Conventional Rail Transit

Systems

The operational process of picking uppassengers and moving vehicles around thesystem is an area where ultralight systems

differ significantly from conventional railtransit systems, resulting in opportunities forenergy and operational cost savings.Conventional rail transit systems generallyoperate as a linear system, i.e., vehicles ortrains proceed down the track in sequence, witheach train stopping at each station andloading/unloading passengers. The NYCsubway system is a rare exception to thisprocess, having express trains that bypasscertain stations in favor of decreasing the travel

time to just a few stations. The NYC systemrequires an additional set of tracks in order tooperate in this fashion. For most conventionalsystems in the world, however, the trains run insingle file along the system, with the averagespeed of the system governed by the rate atwhich the trains can be cycled through eachstation. For an average station, it takes about30 seconds for a train to approach a station andcome to a complete stop, another 30 45seconds to open the doors, unload/loadpassengers, then close the doors, and another30 seconds or so to clear the station withenough margin for the next train to come in.The smallest delay in any of these functionsslows the entire line of traffic, with subsequentnegative impact on the average speed of thesystem. Minimum headways of 1.5 3minutes are the norm when safety margins areincluded. Ultralight systems use a differentoperational process (explained in Section V)that minimizes the effect of local delays,resulting in a positive effect on average systemspeed.

D. Passenger Flow Rates of Conventional

Rail Systems

Capacities of conventional rail systemsvary substantially, depending on the capacityof each vehicle or train, the headway between

trains, and the speed of the trains. The LRTsystem in Portland, Oregon (TransportationResearch Board, SR# 221, 1989) is made up oftwo-car consists with a total capacity ofapproximately 320 passengers (seated and

standing). At their average headway of 5minutes during peak flows, or 12 vehicles perhour, this constitutes a maximum flow rate of3,840 passengers per hour per direction (pphpd).BART, utilizing 10 car consists capable ofcarrying over 1,000 passengers and operating atless than 3 minute headways, has a capacityapproaching 26,000 pphpd. The Paris Metro,using 5 car consists capable of carrying 1,000people and operating at 90 second headways,has a capacity approaching 40,000 pphpd.

III. Capacity and EnergyConsumption of Highways

Highways can also be rated with respect totheir maximum capacity and energyconsumption, thus making it easier to comparethem with rail as a related transportation mode,relative to cost and energy usage. A great dealof research and observation has resulted in theunderstanding that a multi-lane highway has a

maximum capacity on the order of 2,400vehicles per hour per lane (TransportationResearch Board, SR #209, 1994). Consideringthe fact that approximately 95% of freewaytraffic consists of single occupancy vehicles, ahighway lane has a passenger capacity ofapproximately 2,500 pphpd. One can seeinstances, especially on Los Angeles freeways,of groups of vehicles moving at densities of50% or more in excess of this number, but noton a sustained basis or over an extended

distance.Considering only those vehicles that meetthe CAF (Corporate Average Fuel Economy)standards of 27.5 mpg, an average vehiclecapacity of four seats, and an energy equivalentof 40 kWhr/gallon, the energy efficiency of anautomobile is approximately 0.37 kWhr/seat-mile. New technology vehicles such as the


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hybrid powered automobiles by Honda andNissan have decreased fuel consumption by afactor of two or more, for an energy efficiencyof approximately 0.18 kWhr/seat-mile. Theultra-car technology by Dr. Amory Lovins of

the Rocky Mountain Institute (www.rmi.org)promises to increase this efficiency by another50%, or 0.1 kWhr/seat-mile, by achieving afuel efficiency of approximately 80 miles pergallon.

V. Ultralight Rail OperationalCharacteristics

Figure 5 Taxi 2000 Vehicle

The most dramatic and obviouscharacteristic of ultralight systems is the size ofthe individual vehicles relative to conventionalrail vehicles. Figure 1 shows the CyberTran #2Test Vehicle, a 38 foot long vehicle, weighing10,000 pounds loaded, and designed to carry15 20 passengers. Figure 5 shows the Taxi2000 vehicle, designed to carry 3 passengers ata loaded weight estimated to be less than oneton..

A. Computer Controlled SystemsAn important characteristic of ultralight

rail system vehicles is that they are computercontrolled. While this characteristic is notunique to ultralight systems (the Vancouver,B.C. SkyTrain Metro system [Tayler, 1992]and the Paris Metro Meteor line are driverless),in the ultralight systems it is almost a necessity

for any reasonable operating economics. If adriver were required in each small vehicle, theoverhead costs would be intolerable, requiringtrip costs typical of taxicabs without the routeflexibility of taxis. It is this characteristic,

however, that offers the opportunity forsignificant energy and cost savings due to thedifferent operating modes possible.

B. Ultralight Rail Station Configuration

Two important characteristics ofultralight rail systems are the rapidity in whichpassengers can be dispatched toward theirdestination and the speed with which thepassengers arrive at their destination. Both ofthese characteristics are due to a passenger

loading/unloading process known as off-lineloading and direct to destination routing.Off-line loading means that the loading andunloading process takes place off the main line,in a station that is reached by going through arail switch and proceeding to a loading platformwell away from the high speed traffic of themain line. This accomplishes two importantfunctions, the first being that delays in theloading/unloading process at one station do notslow vehicles on the main line, and secondly, bybeing able to maintain a high speed betweenorigin and destination, a vehicle has a highaverage speed over its route. Direct todestination routing means that the vehicles donot stop at intermediate stations between theirorigin and their destination. The ability of asystem to send vehicles directly between originand destination requires that all passengers inthat vehicle are going to the same destination, asituation that can only be realized by usingsmall vehicles in conjunction with high speedand computer controlled direction of passengersto their proper vehicles. Computer control overthe operation of each vehicle, and betweenindividual vehicles, results in headways betweenvehicles of 15 seconds or less. Managers of theMorgantown People Mover are suggestinggoing to 7.5 seconds between vehicles on themain line, and Dr. Edward Anderson, with Taxi


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2000, is proposing running at even smaller timeincrements (Anderson, www.taxi2000.com).The effect of these short headways is to getmore people to their destination quicker, withless energy consuming starts and stops along

the way.C. Ultralight Rail Structures

An important characteristic of ultralightrail is that the structures carrying the vehiclesare much smaller that the bridges, columns,foundations, etc., normally associated withconventional rail transit systems, or evenhighway bridges. This characteristic is the onehaving the most impact on relative costsbetween conventional and ultralight rail

systems. The size of structures required tosupport a 100,000 pound vehicle 15 feet in theair vs. elevating a 10,000 pound vehicle notonly has a dramatic cost effect on theconstruction effort, but also in the amount ofsystem energy it takes to produce the extramaterial and hardware.

D. Power Requirements of Ultralight

systems

A hidden, yet important characteristicof ultralight systems is the low power of theelectric propulsion motors required to move thevehicles around. While rolling friction is lowfor all rail vehicles, the energy required toaccelerate or elevate a vehicle is in directproportion to its weight. This characteristic ofhaving low power propulsion motors is of mostimportance relative to the movement of emptyor low ridership vehicles. Conventional large,high capacity rail systems must move 10s of1000s of pounds of hardware around thesystem even if they are empty or lightly loaded.Ultralight rail systems move much smallervehicles around, and then only the number ofvehicles that are required to meet the passengerload demands. The advantages of this aspectof ultralight rail systems are discussed furtherin Energy Requirements of Ultralight Rail andConventional Rail.

E. Passenger Flow Rates

Capacities of ultralight systems cannotapproach the capacities of heavy metro rail likeBART, NYC, or the Paris Metro, but canprovide the carrying capacity normally provided

by the various LRT systems around the UnitedStates. The capacity of a system like theMorgantown People Mover or CyberTran, bothhaving a capacity of around 20 passengers andoperating at 15 second headways, would be 240vehicles per hour, for a capacity of 4800 pphpd.Morgantown operators are suggesting that thenext upgrade to their system will provide foroperation using 7.5 second headways, aheadway also evaluated for use with CyberTran.Should these headways be implemented, these

two systems would provide a line capacity of9600 pphpd.These headways are based on the

requirement to allow enough time and distancebetween adjacent vehicles so that should theleading vehicle come to a sudden stop, thetrailing vehicle has the time and distance to stopbefore hitting the leading vehicle. With thisrequirement in mind, during high passengerflow conditions, it is possible to slow vehiclesdown and operate under headways even shorterthan the proposed 7.5 seconds. If one reducesthe headway to 5 seconds, a speed of 40 MPHrepresents a separation the length of a footballfield and the safe emergency stopping distanceis less than 1/2 of that distance. An operationalscenario like this results in a passenger flow rateof 14,400 pphpd, which rivals the advertisedcapacity of almost any LRT system, and is fargreater than any actual flow being carried by anexisting LRT system. The Taxi 2000 system isproposed to operate 3 passenger vehicles at aheadway of 0.5 1 seconds for a passenger flowrate of 7200 pphpd.

VI. Energy Requirements of

Ultralight Rail and Conventional Rail

This section looks at the major factorsaffecting the energy requirements of ultralight


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and conventional rail systems and the factorsthat differentiate the energy requirements of thetwo systems.

A. Basic Energy Requirements of Rail

SystemsThere are four primary energyrequirements in the operation of both ultralightrail and conventional rail. These areacceleration, rolling friction, elevation in grade,and aerodynamic drag. Energy requirementsfor acceleration, rolling, and grade changes areall a direct function of the weight of the vehicleand its occupants. Aerodynamic drag is afunction of size, shape, length, etc., andalthough a small force relative to conventional

system acceleration and grade climbing forces,can be a significant energy consumer inultralight systems where vehicle weight is atenth of conventional rail vehicles.

A major expenditure of energy isrequired for elevation change (upward) ofconventional rail vehicles and their loads, andit is in this area that one of the majordifferences in system energy consumption canbe seen between conventional systems andultralight rail systems. It is also the reason thatconventional rail systems, especiallylocomotive powered systems, are limited torather flat grades throughout their routing. Aconventional, 100,000 pound LRT traveling upa 2% grade at 60 MPH requires 240 kW ofpower just for energy associated with the gradechange, plus the energy required to overcomethe rolling friction and aerodynamic drag atthis speed. An ultralight vehicle loaded to10,000 pounds would require only 24 kW tohandle the same grade. In transit systemswhere a series of trailer cars are pulled by alocomotive, such as with Amtrak, all of thegrade drag must be supplied by the tractionof the locomotive. In the case of a train of tencars, each weighing 100,000 pounds, thelocomotive pulling this train must exert apulling force of 10,000 pounds for each degreeof slope of the roadbed (.01grade * 10 cars *

100,000 pounds), plus the adhesion required tomove the locomotive (2,500 pounds for a typical250,000 pound locomotive). BART has four110 kW electric motors per car, for a total of4400 kW for a 10 car train. LRT vehicles

typically have electric motors in the range of400 kW per vehicle. Ultralight vehicles requiremotors of less than 50 kW to meet rolling,acceleration, grade, and aerodynamic energyneeds.

B. Vehicle Weight per Passenger

For rail vehicles not pulled by alocomotive (BART, NYC, Paris Metro, LRT,ultralight systems), the vehicle weight perpassenger is remarkably similar. LRT vehicles

have an advertised capacity in the neighborhoodof 160 passengers and an empty weight ofaround 80,000 - 90,000 pounds (depending onmanufacturer and configuration), for a perpassenger capacity weight of approximately 500- 560 pounds. BART has a vehicle weight ofapproximately 60,000 pounds and a capacity ofaround 120 per vehicle, or 500 pounds perpassenger. CyberTran has an empty weight ofapproximately 7500 pounds and a seatedcapacity of 15 20, or a maximum perpassenger weight of 375 - 500 pounds perpassenger. The Morgantown People Movervehicle is approximately 9000 pounds with a 21passenger capacity, or 428 pounds perpassenger.

C. Vehicle Weight per Passenger vs. Load

Factor

In addition to the similarity of weightsper passengers, all of the rail systems describeduse very efficient electric motors in theirpropulsion systems, albeit of greatly differentpower between the heavy and the ultralightsystems. Therefore, on a per passenger basis,one should not expect much difference in theenergy efficiency of a heavy system and a lightsystem when both systems are operating at ornear their capacity. It is when the systems arerequired to operate at less than their maximum


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loads (which is the case for most systemshaving a morning and evening rush hour), thatsignificant differences can be seen between theoperation of conventional rail systems andultralight systems.

To illustrate the effects of weight,passenger capacity, and operating process onthe energy consumption of a rail transit system,assume an LRT with an empty weight of75,000 pounds and a passenger capacity of 150(@ 166 pounds per passenger), comparing itsoperation with an ultralight system of 7500pound vehicles and a capacity of 15 (to makethe math easy). Table I shows the effectivesystem weight and the weight per passenger ofa conventional and ultralight system as the

ridership drops (assuming constant frequencyfor the LRT and sufficient ultralight vehicles tocarry the ridership.

Table I Effects of Load Factor on Vehicle

Efficiency

Riders/cycle Effective System WeightVehicle Weight per Passenger

Riders LRT ULR LRT ULR150 100,000 100,000* 500 50075 87,500 50,000** 1000 50037 81,166 28,642***2027 60820 78,333 18,320 3750 75010 76,666 9,166 7500 7501 75,166 7,666 75,000 7500

* assumes 10 fully loaded vehicles to carryload at 10,000 pounds per loaded vehicle** 5 vehicles @ 7500 pounds each plus 12,500pounds of passengers*** requires 3 vehicles to carry 37 passengers

Table I shows the dramatic effect ofoperating a system with small vehicles, and onewhich allows the system control to use only thenumber of vehicles/capacity required to carrythe load at any one time. The LRT system isforced to provide an entire, high capacityvehicle even when there are only a few riders,whereas the ultralight system merely provides

enough vehicles to carry the riders. From TableI, it can be seen that the primary energyrequirements of an ultralight system that arebased on vehicle and passenger load weights gofrom equal at full load to only 10% as the

passenger load approaches zero.D. Energy Efficiency of Off-Line Loading

and Direct-To-Destination Routing

Another aspect of operationaldifferences between conventional and ultralightsystems that can have effects on energyconsumption is the ability of ultralight systemsto operate in a full time express mode, i.e.,direct to destination, as opposed to the linearoperating mode of conventional rail, i.e.,

stopping at every station. The standardoperating mode of ultralight systems is with off-line loading/unloading, as described in theprevious section. With an appropriatelydesigned station, an ultralight vehicle can leaveany station and go directly to any other station,in either direction. A conventional linearsystem, however, must start at one end of theline with all of the capacity it will require tohandle the heaviest traffic between any twostations on the line.


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Table II illustrates the effect of thisnecessity for carrying your capacity throughthe entire line versus the option available withultralight systems to only place in service thatcapacity needed to carry the load.

Table II Conventional vs Capacity Dictated

Vehicle Dispatch

Station Passengers FlowEntry Exit Net Required

CapacityLRT ULR*

1 20 0 20 150 30(2 veh)2 50 10 60 150 60(4 veh)3 50 20 90 150 95(7 veh)4 70 10 150 150 150(10 veh)5 20 80 90 150 95 (7 veh)6 10 50 50 150 60 (4 veh)7 5 30 25 150 30 (2 veh)8 0 25 0

Total Capacity Required 485 passengersegments**

Total Capacity Delivered (passenger segments)- 1050 520

* Assumes vehicles carry multi-destination passengers, stop only atstations to which passengers are going,and can reverse direction at any station** One passenger segment is onepassenger transported between adjacentstations

The operational efficiency of eachsystem for this example, defined as thepassenger segments required/passengersegments provided, is 46.2% for theconventional system and 93.2% for theultralight system.

Each unit of capacity delivered carries a

cost in energy as well as wear and tear on thesystem. With each system having a vehicleweight of approximately 500 pounds per unitof capacity, accelerating each of these extraunits of capacity, and carrying them through

any change in elevation, plus the small amountof rolling energy indicates that, for thisexample, the ultralight system is over twice asenergy efficient in carrying the requiredpassenger load. This increased efficiency is due

entirely to the operating options available withthe ultralight system, since the basic weight perpassenger capacity, motor efficiency, andeffects that are a function of weight, such asacceleration, elevation change, and rolling areessentially the same.

An additional effect that is not illustratedin Table II, but can be readily seen as a sourceof additional energy savings, is the savingassociated with not having to stop atintermediate stations. When traffic becomes

sufficiently large, the small vehicles can befilled at one station with passengers destined fora single other station, as opposed toconventional linear rail systems where allpassengers to all stations are in the same vehicleand stop at all stops. This single destinationvehicle then proceeds directly from itsoriginating station to its destination station, nothaving to expend the energy of stopping andstarting at each intermediate station, andtraveling between the stations at a much higheraverage speed. Computer simulations betweendirect to destination routing and linear systemrouting indicate an increase in average systemspeed of a factor of 3 (from 15.7 MPH in thePortland MAX system to 51 MPH in asimulated system with ultralight vehicles).

E. Energy Efficiency Potential from

Intermodal Operations

As illustrated in Table I, high capacity,heavy metro and LRT systems can be veryefficient, energy-wise, when operated at highpassenger loads, and conversely, can beextremely inefficient during periods of lowpassenger flow.


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Figure 6 illustrates the effect of load onenergy efficiency as the passenger loaddecreases in (1) a 150 passenger LRT vehicleand (2) ten ULR vehicles, with the ultralightvehicles being removed from service as theload decreases.

Ultralight rail systems have thepotential to increase the energy efficiency ofhigh speed and heavy rail systems(Transportation Research Board, SR 233,1991) by feeding extra passengers into existingstations from outlying areas off the sides andends of the high capacity systems. Figure 6provides an example of the increase in energyefficiency possible by the intermodalconnection of conventional rail systems andultralight rail, where a single ultralightpassenger load is brought in from the side orend and added to the passenger load of aconventional LRT size vehicle.

Additional passengers brought in fromthe side or ends of conventional systems bysmall ultralight vehicles not only increase theenergy efficiency of the conventional systems,but reduce the need to provide additionalparking in the immediate station area. Parkingfor the ultralight systems can be placed farfrom the conventional system stations in less

expensive and more accessible real estate.Conventional heavy metro and LRT

systems are expensive ($50,000,000 to$100,000,000 per mile) and have a large groundfootprint, two characteristics that detract fromextending the systems into lower densitysources of passengers. Additionally, it is notonly expensive to provide parking aroundstations, where the land is at a premium, but 5acres of expensive parking can only hold about750 vehicles, approximately the passengercapacity of one heavy metro train. Therefore,the first train through the system can take all ofthe parking lot patrons, leaving the stationisolated to many potential passengers andlowering the efficiency of the large transitsystem. Ultralight systems that cost$10,000,000 to $20,000,000 per mile and have amuch smaller ground footprint can be extendedfar beyond the walking limits of conventionalrail stations, bringing additional passengers tothe conventional system in an energy efficientprocess, making the operation of theconventional system even more efficient, sincethe marginal energy cost of additionalpassengers on a conventional system isextremely low.


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F. Ultralight Rail and Cargo Transport

A final point in the spectra ofpossibilities with ultralight rail is transportationof cargo. Ultralight vehicles with a maximumgross vehicle weight of up to 10,000 pounds

have a cargo carrying potential of over 5,000pounds. With a rolling resistance and anaerodynamic drag of an ultralight vehiclerequiring an average power requirement ofapproximately 12 kW, the energy consumptionof an ultralight cargo vehicle can be on theorder of 0.08 kWhr/ton-mile. This valuecompares with a Class 8 truck that can carry 25tons at an average diesel consumption of 6miles per gallon (Charles River Associates,2000), or for an energy equivalent of 40 kWhr/

diesel-gallon, an energy consumption of .266kWhr/ton-mile. While the energy consumptionof highway trucks is approximately a factor of3 times that of a ultralight rail vehicle, themonetary economics of the process is not asdisparate. For an electricity cost of $0.10 perkWhr, the direct energy cost of an ultralightrail vehicle is $0.008 per ton-mile. For a dieselprice of $1.50 per gallon, the direct energy costof truck cargo is $0.01 per ton-mile, only 25%more that the ultralight vehicle cost. This costcomparison is more a reflection of the energypolicy of the United States than of the energyconsumption rates of the two modes of cargotransport. However, when one adds in the costof the truck driver, approximately $0.02 perton-mile, the monetary cost difference betweenthe two modes of transport are comparablewith the differences in energy consumptionbetween ultralight rail and heavy trucks.Obviously, ultralight rail systems would bebest utilized in certain types of high valuecargo such as the U. S. Mail, electronics, orany item with a high time value.

VII. Energy Saving Opportunities with

Ultralight Rail

The above data and comparisonsindicate that significant energy savings are

possible with the implementation of ultralightrail systems. The energy savings of ultralightrail systems relative to conventional rail systemsis due primarily to the ability of ultralightsystems to quickly adjust the number of

vehicles, thus capacity, to the ridershiprequirements. These savings are possible notonly with stand-alone ultralight rail systems, butwith their use as support and passenger feedsystems to high passenger volume conventionalrail systems, such as BART, NYC, and certainLRT systems.The energy savings of ultralight rail relative toautomobiles is due not only to the basicincreased energy efficiency of a steel wheeledvehicle over a rubber tired vehicle, but also due

to the highly inefficient utilization ofautomobiles in congested commuting situations.Table III illustrates the potential effect of

ultralight rail on energy consumption in thehuman transportation sector of the United Stateseconomy. Table III shows the energyconsumption of 4 transportation modes, in termsof their potential (kWhr/available place mile)and in terms of their actual (or best estimated)usage (kWhr/passenger mile).

TABLE III ENERGY USAGE OF

VARIOUS TRANSPORTATION MODES

LRT* ULR Bus* Auto**Potential 0.04 0.04*** 0.14 0.37(kWhr/place mile)Actual 1.14 0.106**** 4.06 1.4*****(kWhr/ pass-mile)

* Data from Portland MAX (TransportationResearch Board, SR #221, 1989)** 4 passenger auto, 27 mpg*** Estimated based on weight and seatscompared to LRT**** Based on dispatching out at 60%occupancy and deadheading back empty***** Based on 1.05 passenger averageoccupancy units of kWhr/passenger mile


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Table III shows that conventional rail andultralight rail are essentially the same in energyefficiency when operated at their maximumpotential, but that the capability of ultralightrail to leave unneeded capacity in the station

has a dramatic effect on energy efficiency atless than maximum loads. Table III indicatesthat in situations where ultralight rail canaugment or be substituted for othertransportation modes, significant energysavings can result, such as with LRT (91%),bus (97%), and personal auto (92%). Whilethere will always be a necessity for buses andautomobiles, the energy consumption numbersindicate that rail in general, and ultralight railin particular, should be implemented as

widespread as possible for the energy savingpotential the technology offers.Not only are significant energy savings

possible with the implementation of ultralightrail systems, but the energy source for thesesystems, electricity, can be generated fromresources under domestic control (coal,hydroelectric, nuclear, natural gas) as opposedto the foreign oil base of the majority of theUnited States transportation infrastructure.

VIII. BIBLIOGRAPHYJack H. Irving (1978). Fundamentals ofPersonal Rapid Transit, D. C. Heath andCompany, Lexington, MAJohn H. Armstrong (1994). The Railroad What It Is, What It Does The Introduction to

Railroading, Third Edition, Simmons-Boardman Publishing Company, Omaha, NBTransportation Research Board, Special Report221 (1989). Light Rail Transit New SystemSuccesses at Affordable Prices, WashingtonD.C.Transportation Research Board, Special Report209 (1994). Highway Capacity Manual,Washington, D.C.Arthur Tayler (1992). Hi Tech Trains,Chartwell Books, Secaucus, NJTransportation Research Board, Special Report233 (1991). In Pusuit of Speed New Optionsfor Intercity Passenger Transport, WashingtonD.C.Charles River Associates, Report D02378-00(October, 2000). Diesel Technology and theAmerican Economy, Washington, D.C.

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