-
The Electric Trolleybus - its role in future
transport systems
P. Williams
log/cow iSyjfem.s' Zfa?,
Email: peterw@logicon. co. uk
Abstract
The trolleybus as a form of passenger transport has survived to
the end of thecentury and in many parts of the world is thriving,
with new developments intechnology helping to create new
opportunities for its increased use. Trolleybusoperation makes
sound economic sense on trunk routes that have the potential
tomaintain and attract consistent growth in passenger usage levels
with reliable andhigh frequency services. The environmental
benefits of the trolleybus areconsiderable and have gained new
recognition in the fight to reduce fossil fuelpollution at the
roadside. Emission comparisons between public transport modesare
provided. Much of the criticism in past years of the visual impact
of theoverhead wiring has become less relevant with the advances in
design oflightweight fittings and suspension techniques, some
examples of which arediscussed. Every passenger vehicle operator
needs to know the true cost ofoperation. In recent years the
difference in costs between diesel and electricpower has swung in
favour of the trolleybus, particularly due to the
latestenergy-saving traction motor controls. Tables derived from a
multi-vehicleoperator are given. Guidelines are offered as to the
requirements for upgradingexisting systems and the implementation
of new installations. The importance ofintegrated transport
policies has never been greater and must be addressed by
allGovernments in the run up to the New Millenium. Intelligent use
of the electrictrolleybus as part of this strategy is
encouraged.
Transactions on the Built Environment vol 33, © 1998 WIT Press,
www.witpress.com, ISSN 1743-3509
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472 Urban Transport and the Environment for the 21st Century
1 Introduction
On a worldwide basis trolleybuses have had mixed fortunes.
Around1930 onwards their suitability as tramway replacement
vehicles had beenrecognised, allowing much of the electrical
infrastructure to remain inplace without major capital renewals.
From a peak in numbers in theearly 1950's there followed a rapid
decline in their popularity as motorbus design and operating costs
showed dramatic improvements.
Much criticism was levied against the trolleybus - it was slow
intraffic, prone to dewirements, expensive to operate (no special
termsavailable on electricity rates) and inflexible in route
extension. Inhindsight, many of these adverse comments have proved
to be purelypolitical and without substance. Poor maintenance
procedures often led toslack wiring and vehicle breakdowns with
little concern for the fare-paying passenger whose perception of
the trolleybus service was one ofunreliability.
However, many operators did not follow the trend to
completeabandonment, choosing instead to retain basic systems and
integrate theminto larger transit operations. Subsequently, in the
1970's and 80'sconsiderable efforts were made to upgrade and renew
vehicle fleets tomake the trolleybus more attractive. In this
present decade majoradvances in traction control techniques and
materials developments haveled to a new awareness of the
environmental and operational benefits ofthe electric
trolleybus.
Transactions on the Built Environment vol 33, © 1998 WIT Press,
www.witpress.com, ISSN 1743-3509
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Urban Transport and the Environment for the 21st Century 473
2 Environmental Benefits
Trolleybuses use electricity as their prime motive power. It is
the onlysource of energy that can be generated by all types of
'fuel' known toman - coal, gas, oil, nuclear fission, water (and
wave), wind, solar andeven waste material combustion. Every fuel
has its own conversionefficiency from primary to secondary (heat)
state, the difference in thesechemical and molecular states being
the direct cause of pollution.Whereas the petrol- or diesel-engine
vehicle creates pollution at theroadside in a random way, that
produced at the power station can be moreeasily contained. Modern
technology can now 'scrub' the emitted gasesto remove dust and soot
particles and filter out noxious fomes.
It is often not appreciated that by fully loading a generating
station theefficiency of energy conversion is increased in much the
same way as theloading of an electric motor. A power station that
runs continuously athigher efficiency can produce additional
kilowatts at much reduced cost.Achieving this status involves
considerable expertise by the generatingauthorities in switching
loads from station to station and so any form ofelectric transport,
usually operating for at least 18 hours a day, willprovide useful
'base load'.
The amount of global motor traffic is increasing at an alarming
rateand the existing road infrastructure and population centre
layouts in manycountries can no longer cope with the volumes. Road
traffic congestion iswidespread with slow moving vehicles creating
pollution at ground levelwhich is not only unpleasant but has long
been considered as harmful tohuman life. Claims that modern
internal combustion engines are 'clean'are often misleading as that
statement is usually made in comparison withthe older, less
efficient engines often and twenty years ago. The
electrictrolleybus, however, emits negligible pollution (Table 1)
and, like thetram or light rail vehicle, can safely run into areas
of high populationdensity, such as city centres and shopping
malls.
The latest generation of trolleybuses being built or proposed
for newsystems combine high efficiency electronic control equipment
with newlightweight traction motor technology. The result is lower
running coststhat outweigh the greater capital and infrastructure
expenditure necessaryto sustain trolleybus operation. In a recent
comparison of vehicle costsone experienced operator found that the
difference between the diesel busand electric trolleybus was less
than 0.1% ( Table 2).
Transactions on the Built Environment vol 33, © 1998 WIT Press,
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474 Urban Transport and the Environment for the 21st Century
Table 1 - Emissions - Diesel Bus vs. Trolleybus
Contaminate
NOx
CO
HCSO 2
ParticipateCO 2
Diesel(gm/km)
18.60
1.90
1.34
1.44
0.561.880
Trolley(gm/km)
1.27
0.06
0.000.62
0.012
1.380
Trolley/diesel
0.07
0.03
0.00
0.430.02
0.73
Per vehicle kilometre (18-metre length): fuel or primary energy
basedSource: Gelderse Vervoer Maatchappij, Arnhem 1995
Table 2 - Operating Costs - Vehicle kilometre
Item
DepreciationInterestMaintenanceMaterialsEnergyTaxesInsurance
TOTALkm (annual)Costs per km
Diesel
56,00019,60016,20015,00042,0004,5002,000
155,30060,000
2.58 (100%)
Trolley
66,00035,00021,60012,00018,000
-4,000
156,60060,000
2.61 (101%)
Tram
93,00098,00042,00031,00027,000
-6,000
297,300
70,0004.24 (164%)
Figures are in Dutch GuildersSource: Gelderse Vervoer
Maatchappij, Arnhem 1995
In the case of Arnhem, acknowledged as one of Europe's
leadingchampions of the trolleybus, a fleet of 51 modern
trolleybuses operateson a 55km system of five routes. The operator,
GVM, attributes 10%additional ridership directly to the presence of
trolleybuses, which areactively and positively marketed. Public
perception of the trolleybuses ishigh and there is a strong sense
of 'ownership' of the system.
Transactions on the Built Environment vol 33, © 1998 WIT Press,
www.witpress.com, ISSN 1743-3509
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Urban Transport and the Environment for the 21st Century 475
3 Trolleybus Trunk Route Planning
With operating costs now comparable with the diesel bus it is
importantthat the additional major capital expenditure on the fixed
electricalinfrastructure is recovered as quickly as possible.
Applying trolleybusesto trunk routes that have the most potential
for high passenger usage andconsistent growth in revenue is the
only way to achieve this. Carefulplanning of these routes is
therefore essential, the aim being to carry morepassengers at a
lower system cost.
Certain principles in route planning should be applied:
• Most direct route from outer termini to city centre or
businesscomplex.
• 'Key' stops at approximately 500 metres distance.
• Ability to achieve high average speeds to reduce journey
times.
• 24 hour bus-only segregation lanes.
• Fully integrated traffic light control at major junctions
andintersections.
• Reduction in complex overhead wiring layouts.
• Passenger inter-change facilities with 'feeder' routes (diesel
bus).
• Capability of running high capacity articulated vehicles (up
to 18metres length) through central areas.
• Electronic ticket cancellation to reduce boarding times.•
Park-and-ride facilities near outer termini.
• Minimal competition from other transport operations.• High
frequency of service during peak hours.
The installation of the wiring on the trolleybus trunk routes
should beto the highest standards to allow high-speed passage of
the collectorheads through the overhead points and crossings, thus
reducing the risk ofdewirements. Visual intrusion of the overhead
can be minimised by theuse of lightweight modern fittings and
support catenary.
In a survey conducted by the Vancouver Transit Commission in
1996it was found that users of the existing trolleybus services
were supportiveof a modernisation programme provided that the
frequency and reliabilityof operation was increased and routes were
extended or diverted to servemore business and shopping areas. The
trolleybus service was consideredto be the preferred means of city
centre travel and the financial outlay toachieve full integration
was not seen as an obstacle to progress.
Transactions on the Built Environment vol 33, © 1998 WIT Press,
www.witpress.com, ISSN 1743-3509
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476 Urban Transport and the Environment for the 21st Century
4 Trolleybus Infrastructure Requirements
To support trolleybus operation a fixed infrastructure will be
requiredwhich for costing purposes should have a design life of at
least 15 years.This timescale will ensure that an adequate return
on investment isachieved before replacement becomes necessary.
Quality of manufactureand installation must be high but there is
little merit in over-engineeringfor longer life as advances in
technology may well bring with it savingsthat can be incorporated
at a later date on an existing system
Equipment for trolleybus operation can be summarised as
follows:
1. Depot/Office/Workshop - existing building (modified)
orpurpose built.
2. Sub-stations - rectification of AC powersupply to 600 or 750V
DC.
3. Cabling/Section Switching - distribution of DC supply.
4. Overhead Wiring - lightweight, fully automated.
5. Communications - intelligent traffic managementand route
selection system.
6. Stops/Shelters/Displays - passenger information
andcomfort.
7. Computer system - SCADA for data logging ofvehicle movement,
passengernumbers, energy consumption.
8. Maintenance Plant specialist service equipment.
Transactions on the Built Environment vol 33, © 1998 WIT Press,
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Urban Transport and the Environment for the 21st Century 477
5 New Approach to Wiring
With the many advantages of electric trolleybus operation comes
thedisadvantage of having fixed wiring, which may be perceived as
visualpollution of the skyline. It has, therefore, become essential
to reduce theweight and size of overhead components and this is
being achieved bymoving away from the traditional cast brass or
iron castings to extensiveuse of modern materials. Investment cast
stainless steel and aluminiumbronze fittings are almost half the
weight of the old designs and cheaperto manufacture. Their lighter
weight can be supported and fixed inposition by parafil rope
cross-spans or stainless steel span wires.
Parafil rope has been used successfully on some recent light
railinstallations but appears blacker in colour against the sky. It
also has asmaller thermal stability range than stainless steel and
can thus 'go slack'in high ambient temperatures causing problems
for trolleybus operationwhich demands rigidly held overhead wiring
at all times. Its lower initialcost is offset by the greater
long-term maintenance requirements such thatit is likely that all
future trolleybus installations will use lightweightstainless steel
in their construction. Roadside (or traction) poles can nowbe
reduced to the minimum possible diameter and combined with
streetlighting wherever possible. In city centres it is infinitely
more practicalto use span wires anchored to buildings with eyebolts
and avoid polesaltogether.
Points and crossings have been designed which offer the
maximumdynamic reaction with the twin overhead collector heads
mounted on theroof of the trolleybus, enabling them to be
negotiated at higher servicespeeds than with the previous cast
brass and iron designs. Routechanging is done by electric solenoids
commanded by switching circuitsin the overhead or by radio signal
from the vehicle.
Transactions on the Built Environment vol 33, © 1998 WIT Press,
www.witpress.com, ISSN 1743-3509
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478 Urban Transport and the Environment for the 21st Century
6 Trolleybus Design and Construction
In several countries the trolleybus is already an advanced
vehicle withsome of the latest articulated models having seats for
40 — 50 passengersand up to 100 standing in an overall length of 18
metres. Its peak loadingcapacity is therefore considerable when
combined with high frequencytimetables. Rapid acceleration with
full loading means that the trolleybuscan maintain intense services
on trunk route systems.
All new trolleybuses should use the latest technology in their
designand construction but it must be emphasised that 'too much too
soon' canproduce reliability problems which must be avoided if
credibility of thistransport is to be retained. One particular
feature that will do much toenhance acceptance is the low floor
design with 'kneeling' action thatfurther reduces step height at
stops. Reliability of the actuating systemnecessary to provide the
lowering has improved greatly in the past twoyears with much of the
development work happening in the UnitedKingdom.
It will be of importance to existing and future operators of
trolleybusesto have standard vehicles available that can be 'batch
produced' to reducethe initial purchase costs. Manufacturers need
to consider that both leftand right hand drive trolleybuses will be
required and the two optionsshould be without cost penalty to the
operator. Standard specificationvehicles can readily gain
individuality by the use of modern colourschemes and graphics. A
typical 'International Design' trolleybus maybe as shown.
Basic configuration Single-deck ArticulatedPassengers (including
standing) 140Overall length 18 metresOverall height 3.5 metresMotor
Size 2 x 65kW AC AsynchronousControl Electronic AC InverterBraking
Regenerative and dynamicAuxiliary Generator 55kW continuous
ratingDriver Control Intelligent graphic terminalNumber of axles 3
(2 driven)Maximum speed (full electric) 65 kphMaximum speed
(generator only) 28 kphUnladen weight 17 tonnes
Generator operation should be considered viable for limited
'off-wire'use only such as temporary diversions due to roadworks
and depotmanoeuvring. This is not to be confused with the full
Duo-bus option.
Transactions on the Built Environment vol 33, © 1998 WIT Press,
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Chopper block .Onboard power converter
Guiding device emergency pump ' Traction motor CHVEK512533
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480 Urban Transport and the Environment for the 21st Century
7 Funding Trolleybus Set-up Costs
The following costs are based upon recent research (Logicon
Systems Ltd1997) into the requirements of a modern trolleybus
system. For thepurposes of this research it was first necessary to
establish the criteria fora 'typical' new turnkey trolleybus
network which, after consultation withpotential manufacturers and
suppliers, was agreed as follows:
An installation of 50km of double-track overhead wiring, on five
routesradiating out of a city centre, each with crossings and
switches atjunctions and branches. Intelligent route and traffic
control throughout.10 minute peak headway on all routes requiring
25 trolleybuses of 140-passenger capacity (initial system capacity
of 20,000 passengers/hour).
Table 3 - Initial Costs
Item
Consultancy and design
Electrical sub-stationsElectrical cabling worksDiversion of
servicesOverhead Wiring
Depot/workshop (existing)Communications /SCADA
TrolleybusesPassenger stops/sheltersMarketing/contingency
TOTAL
Cost GBP0.7M
3.5M
3.0M3.0M7.5M3.0M3.8M7.5Ml.OMl.OM34.0M
Cost USD1.1M
5.6M4.8M4.8M12.0M4.8M6.1M12.0M1.6M1.6M54.4M
Cost DM2.0M
10.0M8.5M8.5M21.4M8.5M10.8M21.4M2.8M2.8M96.7M
Governments have the opportunity of proving their
genuinecommitment both to reducing private car dependence and
improving theenvironment by directly funding new trolleybus
installations. Wherethere is merit in encouraging investment from
the private sector then thisshould be confined to the operation of
the fleet. Obstacles to profitabilitymust be reduced to a minimum
by, for example, restricting competitivepublic transport operations
and private car journeys into town and citycentres.
The electric trolleybus should play a key role in the
internationaltransport industry to provide the passenger with
quality, reliability andeconomy. Logicon Systems Ltd is a major
advocate of this policy and isavailable to advise and assist in
this objective.
Transactions on the Built Environment vol 33, © 1998 WIT Press,
www.witpress.com, ISSN 1743-3509