Claverton Light Rail 24 Oct 2008

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Claverton Conference 24/26th October 2008

SUSTAINABLE LIGHT RAILBy Prof. Lewis Lesley

SUMMARYIn an increasingly urbanized world most personal journeys are made in townsand cities and are relatively short, in UK 75% under 8km long. In the developedworld, the motorcar dominates these trips. Car drivers will however transfer sometrips to rail. Electrically powered light rail (or tramway) is an economic means forsatisfying many short urban trips. Light rail can be constructed with a minimum ofurban disruption and when coupled with renewable generation is energysustainable. It also has a much smaller carbon footprint, when diverted car tripsare included, than any other mode except bicycles.

1.0 Definitions

Light rail is a passenger transport system using steel rails to support and guideelectrically power vehicles, running on street with other traffic and on separatededicated lines. Normally light rail is driven on sight without railway signaling, soit can share road space or road alignments, and mix safely with road vehicles.Ideally light rail should enjoy 100% priority over other traffic, through dedicatedlanes and the pre-emption of traffic lights. Sustainable light rail emits no CO2 inthe operating cycle, using renewable generation. When attracted car trips are

included, light rail reduces total CO2 emissions. It is also financially viable so not

vulnerable to public spending squeezes.

Consistent market research and experience over the last 50 years in Europe andNorth America shows that car commuters are willing to transfer some trips to railbased public transport but not to buses. Typically light rail systems attractbetween 30 and 40% of their patronage from former car trips. Rapid transit bussystems attract less than 5% of trips from cars, less than the variability of traffic.

2.0 Unsustainable energy and transportThe present UK energy consumption mix and its growth, is based on increasinguse of fossil fuels. Not only are these fuels, and in the case of transport use, verydependent on oil, which is expected to peak in production soonest compared toother fossil fuels. As importantly whilst stationary users of oil can convert to otherfuels and indeed to renewable energy sources, most transport, especially road

transport has no obvious alternative power system which can be economicallyimplemented.


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Fig. 1

It should be noted that whilst total energy use over this period has been nearlystatic, solid fuel use has decline gas increased, and oil has been static as the

decline in the use of oil for electricity generation, has been matched by the

growth of (road) transport use.

Fig. 2 Change in energy mix 1990 to 2001

Fig. 3. Energy end users 1990 to 2001

Transport energy consumption is almost equal to oil consumption.


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Fig. 4 Growth of transport energy use

Road and air travel are almost entirely responsible for the growth of energyconsumption in the sector.

Fig. 5 Modal use of energy in road transport

In road transport, nearly two thirds of energy use is for private cars, with goodsvehicles accounting for another third, leaving all other modes of road transportusing only 3%.


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Fig. 6 Consumption of transport services

Considering the use made of different modes of passenger transport, thedominant is private car, accounting for about 800bn passenger km. pa. The nextare an order of magnitude less, bus and rail, each with about 80bn passenger

km. It is worth noting that rail has increased slightly over a 30 year period, whilst

bus use has declined by iver 10%. Air has grown from the least mode in 1970 tothe fourth used mode at about 10bn passenger km pa, with motor and pedalbikes being about 6bn km pa.

Fig. 7 Transport greenhouse gas emissions


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Fig. 7 shows air transport as the most serious greenhouse gas emitter becausethe Department for Transport has failed to include private car use, which wouldbe an order of magnitude off the scale about 500million tones pa, and is the mainreason the UK will fail to hit its EU emission targets, without a serious effort yodivert car trips to less polluting modes.

Fig. 8 Public transport greenhouse gas emissions

In comparison to the other modes of transport, the greenhouse gas emissionsfrom public transport are trivial. This comes out more clearly in Table 1.

Table 1. Transport % of UK Greenhouse gas emissions

Emitter 1990 1995 1996 1997 1998 1999 2000 2001 2002All

Transport

118 127 136 140 146 149 153 151 151

Public

Transport

8 8 8 7 7 7 7 6 6

UK Total 777 729 756 738 737 707 712 719 697

%Transport 15% 17% 18% 19% 20% 21% 22% 21% 22%

Whilst transport in both absolute and relative terms represents a growinggreenhouse emitter, public transport modes have been reducing emissions inabsolute terms, representing only 4% of all transport greenhouse gases.

Considering in detail how private cars are used (Fig. 9), shows that most trips are

short, and that less than 3% of all trips made are over 50km long. The potential istherefore great for switching short car trips to better public transport (or cycling),where the journey time differences are small.


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Fig. 9 Trip length distribution of car travel.

The data presented in this section shows that transport is a large and growingconsumer of fossil fuel, that transport is highly dependent on (imported) oil, andthat transport is a growing emitter of greenhouse gases. For passenger travel,

the car is the dominant mode and emitter of greenhouse gas, but the majority of

car trips are short. Such short trips can be attracted to better public transport.Can market research provide a guide ? Throughout the industrial world, cardrivers are willing and do switch to rail. An insignificant number are willing toswitch to buses. The reasons for this reflect perceptions and experience ofservice speed, reliability, travel comfort and social acceptability. HistoricallyMetros have been seen as the way to give metropolitan areas high quality railsystems. Light rail however has been shown to give about 90% of the benefits of

Metro at about 10% of the investment cost. This is particularly so when trafficmanagement measures are implemented to give light rail priority and reduce theavailable road capacity for private car use.

3.0 Modal shift to light rail

It follows that light rail lines should be built parallel to the busiest roads, with thehighest volumes of car traffic. Only by diverting car trips will light rail reduce

urban greenhouse gas and pollution. Building light rail to serve areas of low carownership or high unemployment will rarely make significant ecological

75% of trips < 8km

50% < 5km25% < 2km3% > 50km


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contributions.

People drive cars for among other reasons their convenience, speed anddependability. Despite the rising cost of fuel, cost is rarely the most importantfactor in car use. Using taxis is usually cheaper than having a car. For light rail to

achieve significant market penetration, journeys must be fast, waiting times shortand operations 100% reliable. As a rule of thumb people will not wait for longerthan the ride time, since it would usually be faster to walk. For short urban trips ofunder 10mins, the service interval needs to be less than 10 minutes, ideallyabout 5 minutes, giving an average wait of less than 3 minutes. A no timetable,convenient, turn up and go service is the first requirement to attract committedcar users.

Fast journeys need direct routes and high operating speeds. Light rail service

speeds should be above 25km/hr. Here there is an interaction with stop spacing.

Closer stations mean shorter walks but a slower operating speed. Widely spaced

stations mean longer walks but a faster speed. The local population density willdetermine the optimum stop spacing, to minimise overall journey times, and givea competitive alternative to car use. This optimum will also maximise catchmentsand hence patronage, and depending on fares, revenue.

Park and ride is vital both for maximising the attraction of external car trips,reducing traffic and raising patronage. The factors on the siting of park and ridestations are well determined and proven in practice. The terminals of tram linesmake good park and ride stations, since there will usually be a tram waiting to

depart, which is important in maintaining passenger confidence. Such terminals

will be sited either on the edge or slightly out of town. This would make theinstallation of wind generators acceptable, and provide renewable power.

4.0 R & D for sustainable tramways

Tramways have developed incrementally over the last 150 years. Recently thetrend has been to use modified heavy rail technology, which has increased costsand the weight of trams. This paper concentrates on vehicle technology, althoughother aspects of tramways have also been addressed to reduce costs or improve

performance, especially track and power supply systems. The increase in weightper passenger space has been noticeable in the last 20 years. Contemporarytrams have masses of about 200kg per passenger, compared to 125kg forbuses.


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Table 2 Comparison of vehicle weight per passenger

Type of Public Transport Unladen kg No. ofpassengers

Kg perpassenger

Bus

Single deck rigid 9000 53 170Double deck 12000 84 143

Articulated 18000 140 129

Trolleybus 13000 100 130

Train

Metro car (electric) 32500 150 216

Suburban (diesel) 35400 120 296

Tram

Tatra T5C5 19500 100 195

Manchester Metrolink 46000 200 230

Sheffield Supertram 54000 220 245City Class 22000 200 110

After Lesley 1994

With frequent start and stops of urban operations, most of the energy used is dueto mass and maximum speed.

Kinetic Energy = 0.5mv2 equ. 1

The two critical variables in urban transit energy use are vehicle mass and themaximum speed. Many designers have tried to capture braking energy to reduce

overall consumption. Electrical regeneration into batteries or back to the powergrid, or mechanically, e.g. into flywheels, have produced at best 25% powerreductions, ignoring any weight penalties from this equipment. Halving the tramweight will automatically halve power consumption.

Reducing the maximum speed can be achieved by optimising stop spacing andusing the maximum rate of acceleration that is ergonomically safe for standingpassengers. Most trams accelerate at about 1.0m/s2. Trams that can accelerateat 1.8m/s2, on a 400m stop spacing, can reduce the maximum speed needed by

3%, to achieve the same operating speed. A 3% lower maximum speed means

6% less energy used per start stop cycle.

Historically trams had steel under frames and wooden bodies for a low mass.Learning from the automotive and air industries, all metal integral bodies canhave the same mass per passenger space as wood but be much stronger andsafer.


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Although low voltage dc power systems still supply tramways, the operatingvoltages have increased from 500 to 750. This means that the current used hasnot increased in line with tram weights, since

W = IV equ.2

Increasing the voltage by 50% means the current has only increased by 33% fortrams twice as heavy. Nevertheless a contemporary 40 tonne tram will drawabout 1400amps when accelerating. This creates a large voltage drop betweenthe tram and substation, reducing performance, and to increase the number oftrams operating means strengthening the substations and power distribution.

Originally trams were powered by dc motors using variable resistors (rheostats)for acceleration, another source of energy wastage in heating resistances. More

recently power transistors were used to chop the dc voltage, to give variable

voltages and so vary motor speed. Today most trams use ac motors powered by

variable frequency and variable current inverters, fed from the dc Overhead Line(OHL).

The market for tramcars is limited, with a world production of less than 1000annually. In comparison over 100,000 buses are built annually, so can afford toinvest in product development, and in comparison to trams be more technicallyinnovative. This is compounded by the replacement cycle for buses beingtypically 10 years, and 30 years for trams (70 in Blackpool). In comparison toprivate cars, trams appear obsolete long before they are worn out.

Fig. 10 Tram still running in Blackpool after 100 years


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Even at the most optimistic levels of investment in new tramways, the vehiclevolumes will not be large enough to support mass production, the usual way toreduce unit costs. The TRAM research project begun in 1988 has turned thislogic around by identifying mass produced components off the shelf (COTS) fromother industries, that can be used unmodified on trams. The challenging part has

been to manage the interface between different standard components, and therail environment, which in some aspects is kind and in others harsh.

The R&D process began with simulations and calculations, progressed to benchand laboratory testing, then the construction of a slave vehicle using a redundant1930!s tram in Blackpool. Finally a full size prototype vehicle was built and testedin Blackpool. From that experience, the tram was rebuilt, re-equipped with thenext generation COTS and tested in Birkenhead and Blackpool.

Fig. 11 Slave tram being fitted out at Carnforth Depot

One of the advantages of COTS is that the original equipment manufacturers

(OEM) are engaged in constant product improvement. This means the trambuilder can piggyback on that to achieve more advanced vehicles with aminimum of investment. As an example the power train COTS used on the CityClass tram has a high level of energy efficiency, and continuous poweroptimisation to reflect varying vehicle loads and track conditions. In overall terms,the power train is better than 90% efficient.


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Fig. 12 Prototype tram at Fleetwood on clearance tests

A team from the Electrical Engineering Dept. of the University of Manchestermeasured power consumption and compared it with other contemporary trams.(TABLE 1). This found the city class uses significantly less than similar capacityand performance trams, and less even that smaller, lighter but older trams inBlackpool. Part of the reason for the higher energy efficiency is of course lower

vehicle mass, and part through the advanced power electronic COTS.

Table 3 Power consumption of various tramcars

Tram type Weight (tonnes) Power use (kWh/km)

Blackpool Centenary 18 1.5

Manchester Metrolink 46 4.1

Croydon Tramlink 38 3.9

Sheffield Supertram 54 4.5

City Class 22 1.0


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Fig.13 Prototype at Blackpool Pleasure Beach 2006

5.0 Application projects

How do new capital technologies get introduced when the market is dominated

by the public sector, where a minimum of three previous satisfied customers areneeded ? We might reflect how quickly mobile phones would have beenintroduced in Britain, if telecoms was still a monopoly of the GPO ? This Catch22 can be broken by private sector initiatives, where the risk is taken by theinvestors, who then get the rewards from commercial projects.

Changing the fundamental economics of tramway projects, away from asubsidised public sector controlled environment is however the subject of anotherpaper ? Suffice it to say that privately funded projects are being progressed,

which will enable the rate of new tramway projects in the UK to increase from theaverage of one every 4 years achieved over the last 20 years of public funding, to

several a year. It might thus be possible to catch up with German levels oftramway provision in 20 years, rather than 150. Several of these privately fundedprojects are linked to complementary renewable power generation, making thetramways energy self sufficient, zero CO2 and when attracted car trips arefactored in, a net reduction of urban CO2.


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Fig. 14 Coping with steep hills and tight curves in Birkenhead

6.0 Conclusion

To reduce CO2 in urban travel, significant numbers of car trips must be attractedto public transport (or cycling ?). Buses have not been able to achieve that, andalso need imported fuels that add to CO2 and other health threateningemissions.Tramways are proven worldwide to attract up to 50% of their patronage from carusers. Technical R&D to improve the efficiency of trams, with the adoption of

COTS to reduce costs, makes new tramways CO2 reducing and give value formoney. With the reduction of the cost of Photo Voltaics, and better power densitybatteries or super capacitors, the roof of a tram is big enough to be therenewable power generator, not needing any other power supply. That however

is the subject of another paper, and the technology is some way in the future.


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Fig. 15 New city class tram nearing completion at Blackburn factory 2008

References

Lesley.L, Winstanley. A, Renfrew. A, Barnes.M and Chymera. MPower Consumption in a new LRVRailway Engineering June 2007, ISBN 0 94 7644 61 10

Lesley.L,City Class LRV,The Rail Engineer No. 27, Jan 2007

Lesley. LAffordable Mass Transit ?Mass Transiot, Washington DC, Feb 2005

Lesley. L Contributor

Improving public transport in England through light rail,National Audit Office. 19th April 2004


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Lesley. L,Light rail value for money ?Report to National Audit Office. Feb 2003

Lesley. LThe role of rail in European public transport.PTIU Seminar, Shire Hall Mold, 6th Dec. 2000

Lesley. LProgress with the TRAM low weight LRVLight Rail 94 Conference 8-10 November 1994Proceedings Published by Transport Science Ltd. ISBN 0 906442 21 3

Revised 5th Dec. 2008

Claverton Light Rail 24 Oct 2008

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