Use of Electric buses to improve Environmental performance ofbus travel by Sagar ShahIntroductionIn recent years there is a ton of hype around electrificationof cars and which is right for a reason that they contribute a lot tocongestion and there is huge amount of emission of major pollutants which hasmade the urban air quality a big concern.But here’s a less considered fact: Personal vehicles are probably the most challenging to electrify cost-effectively as they just traverse at maximum 4 people over a small distance in a 2-ton vehicle which consumes a lot of energy. The case for electrification or introduction of an alternate fuel is strong for other vehicles & Public Urban Buses top the list.In this paper I will be exploring the implementation of electric buses to improve the environmental performance of Urban bus travel as well I will discuss various considerable points such as cost effectiveness of the electric bus as well as legislations, modifications in the regulations concerning the application of electric bus to the various markets of the world. The paper deals with Battery electric buses which will be referred to as BEBs for the rest of paper.Why Battery electric buses?Buses are the most important mode of transport all over theworld when public transport is considered. Buses for long have been used as amain mode of transport for medium to short distance travel and have been themost effective as they go through various routes. In March 2017, there were anestimated 4.93 billion bus passenger journeys in Great Britain which is around60% of all public transport journeys (DfT, n.d.)[1].When talking about greener transport public bus transport are one of the worst contributors to two main contributors to air pollution namely CO2 and NO2. The emission of oxides is a result of fossil fuels used to run the conventional buses. Most of the conventional buses run of diesel. It is found that public transport buses use 40,000 litres ayear which is 100 times more than a normal car. They run for 16-18 hrcontinuously as compared to a car which has a usual use of 2 hrs. For thisreason, it is important buses are electrified as soon as possible.Past development and Current scenarioFor the last two decades there has been large developments inmaking the electric vehicles a reality. It’s a tough task to design a bus whichcan continuously work for 16-18 hrs and carrying passengers as much as the conventionalbus does. It is a known fact that all over the globe initiatives have beenundertaken to introduce electric buses. The first uses of were mostly small, mini or midi-buses. Theimprovements of battery technology from around 2010 led to the emergence of thebattery bus, including heavier units such as twelve-meter standard buses &articulated wagons. Let’s have a look at the history of battery electric busdevelopments throughout the years.In 2009, Shanghai catenary bus lines began to use battery buses.In September 2010, BYD Auto began manufacturing BYD K9.In 2013, battery buses introduced in Netherlands.In Germany in 2013 battery buses undergoing tests in Bremen and Bonn.The largest bus fleet in Dallan, China included 600 BYD buses.In 2015 BYD launch the first double decker battery buses.Botosani, Romania planned for public transport to operate fully electrically at a conversion cost of 20 million EurosFigure 1: BYD Double decker busIn October 2015, the double decker buses were converted to BYD electricswith a range of 250km. London’s centre city access toll waived off for batterybuses[2] (Wikipedia,2017).It has been some very successful pastyears for developers and there is a huge move towards electric bus seen allaround the globe. The quality of urban air is deteriorating and with citiesgrowing and urbanisation on the peak it becomes very important to have a cleanfleet of buses which can be cost effective and non- polluting at the same time.Transportation PoliciesLondon the capital city of theEngland has for long been the economic hub and has been an example for theworld in terms of providing good public transport. The city is very well knownfor its one of the best public bus services provided to its citizen. In thepast few years the air quality levels have been one of the most significantworries for the policy makers. A study by Kings College shows that there arealmost 9500 people who die because of the air pollution. The NOx andthe PM(2.5) have been the biggest contributors to the air pollutionand they are highly emitted by the burning of fossil fuels by vehicles. COxis the biggest contributor to greenhouse effects and they are the largest heatabsorbents and have caused a heavy increase in the global temperatures withmore and more emission of GHGs. With all these in mind considering the Londonbus network there has been drastic steps taken to curb down the emissions andgo forward towards Zero Emission. Because of which following policies areundertakenTheMayor of London announced a new £86.1m programme to cut harmful emission fromLondon’s existing bus fleet.Around5000 buses more than half set to be upgrading to meet the Ultra-Low Euro VIEmissions standards, cutting pollution by up to 95%.TheMayor has also set out in his draft Transport strategy that by 2037 at thelatest, all 9200 buses across London will be zero emission.Theelectric routes are part of major transformation the Mayor has asked TfL todeliver to reduce emissions from London’s bus fleet.Oneother important policy to clean up the Capital’s bus fleet include the phasingout of diesel only buses& a commitment to purchase only hybrid or zeroemission double decker buses from 2018.Theintroduction of 12 new low emission bus zones, operational by 2020, this willsee NOx emissions along routes fall by more than 80%.InMarch 2017 TfL has introduced the first of 12 low emission zones, where onlybuses meeting the toughest standards are permitted to run.Usingmore Electric buses can dissolve the problem of greener transport &congestion.To take a view of what the polices are doing on ground andwhat people think about the current air quality situation in the city a pollwas conducted & designed by YouGov for a sample of 1000 Londoners. (YouGov, 2017). The results of the poll are discussed here:88% think air pollution is a big problem, with 66% citing airquality as bad and 72% wanted more stringent actions to curb air pollutions.[3]This shows that even after the polices being so hard people are still concernedmore about the quality of air they breathe in when on streets of London.As from all of this it is quite evident that the best busnetwork in the world has outlined large number of policies & taken giantstrides towards making buses run by electric batteries. A lot of potential isseen in the much anticipated zero emission buses to take over and make the citya place to breathe freely in near future.Key benefits of Battery electric Buses(BEB’s):Electric battery buses bring with them lots of benefits. Mostimportant of them are the environmental benefits which will be talked moreabout later in this paper. Following can be listed down as the major benefits:Air quality improvement This will happenlargely because of the zero tailpipe emissions from the BEB’s. The levels of COxand NOx in the air are quite worrying in certain cities which ispredominantly around the city centre. BEB’s work on the principle of zero tailpipe emission this should create a better ambient air quality for citizens.Noise Pollution reduction Electric buses arevery quiet in operation and can be a big advantage in urban areas to reducenoise pollution when compared to highly noisy diesel engine buses. If weconsider a peak hour rush in a urban street with lots of vehicles, electricbuses would contribute zero to noise levels as they can be near to perfectquite when in operation.Journey Comfort Electric buses havebeen told to be very comfortable while on the move with passengers as itreduces the jerks due to braking as it uses regenerative braking. The buseshave a lot more space when compared to diesel bus as they don’t have to beequipped with heavy engines and other mechanical parts. The buses are muchlower to the ground and can also be a aid to disable people as it is very easyto get on and off the busMaintenance cost Savings Due to very lowmechanical instruments needed for the propagation the wear and tear is heavilyreduced which can save a lot of money over the lifetime of the bus whencompared to conventional diesel buses.DrawbacksRangeFor a large period, there has been a great enthusiasm towardsmaking public buses run on battery electric buses, but the hindrance is thatbuses need to run 16-18 hrs continuously & there need to be enough power inthem to run all day long, but the range of the buses is limited &0 can onlyrun on smaller routes & not many double decker buses are operational tilldate. Most of the buses are charged overnight and take almost 3-5 hrs to chargefully and run for the whole day.Heavy weightTo power a large vehicle like the bus there needs to be alarge battery pack inside the bus. The most famous BYD auto designed K9 with ahuge 345 kwh battery. The energy density is just near 100wh/Kg which means thebattery pack itself will be 3.5 tons. (Independent, 2016)High initial costsThe cost of Conventional diesel buses is almost the half ofthe BEB’s. This factor for a big span of time made BEB’s not feasible. But withhigh research and development and a great downfall in the price of the batteriesfor buses has somewhat narrowed the gap between the ownership costs of theBEB’s and Conventional diesel buses. In future with more and more investment inthe research we can expect to see more drop in the price for electric buses andit can be said that they will be more affordable by more markets.Battery replacement costsBatteries are the most important component of the BEB’s. Costof the replacement of batteries can be a very daunting factor when economicviability is considered for the electric buses. As the costs of battery packare very high and the size needed for the bus is a huge one so can almostresult in somewhere around £20k after a span of 6-7year depending on themanufacturers. But recently many companies have claimed to make this costdiminished as the give a 12-year warranty of battery packs included in the busand which can be considered as the average life span of a bus.Infrastructure Re-DevelopmentA shift from one technology to another can prove to be a veryhard process. Electric buses would need charging docks for the buses to chargeovernight. This will need significant amount of money and it will add up to thecity’s electric demand.Research in Battery Success or failure of zero emission buses largely depend onthe success of the batteries used for electric buses. The reports on the highlyhyped London electric double decker bus which is manufactured by the ALD &BYD as a joint venture which has the technological input form BYD, which isworld’s pioneer in BEB’s. (TFl, 2017) This BEB’s uses as345kwh battery pack. BYD for long has specialised in a type of Lithium batterycalled Lithium Iron Phosphate(LiFePO4). It is reported to have an energy density of just around100wh/Kg. So, this battery pack will weigh a tremendous 3.5 tons before anypackaging, interconnects, cabling or BMS are considered so a weight of 4 tonsis more likely. The other drawback of LFP type batteries is its abilities totake & release charge.Now, to make the battery much more light and efficientdevelopments can be made in the direction of changing the materials used in thebatteries. For example, Tesla using lithium Nickel Cobalt Aluminium(NCA) theP90D model S has a 90 Kwh battery pack which has an energy density of 140wh/kg.Definitely this was for a car, but such developments must be made, and a lotcan be achieved in the electric drive technology of the electric buses.Economically Feasible????The idea of battery electric bus is viable or nor largelydepends on its economic feasibility. Any new technology at its advent isexpensive & is not affordable by all. For example, when smartphones startedto roll out they were priced highly when compared to the conventional mobilephones. But with heavy investment in research & development & alsolarge competition around the globe to consumer markets the prices have comedown & the market has reached to a new pinnacle every year. Figure 2 Drop in Battery Prices over the last decade and future projections Battery electric buses can also beconsidered more as an electronic entity rather than an automobile with more andmore research & the urge to go green on immediate basis will see a largevariation in the current buses & the buses to roll out in next 10 years. Figure 3 Citi research Li batteries price drop. As shown is the figure it is quite evident that due to heavyturnaround towards electric vehicles there has been a drop of 80% in the priceof the main component of BEB’s battery packs. Prices have dropped yet theinitial cost is very high to own a battery electric bus having a range of 250miles. With the change in technology there will be a need to improve theinfrastructure. This can add to the overall cost in bringing more BEB’s to theroads pertaining the charging technology adopted, and the nature of changeneeded.Going forward it becomes necessary to study the feasibilityof BEB’s to make the electric buses accepted very firmly.Transportation economy vary quite too much in every part of the world largely because of the different application of bus transport in every urban city. Table 1 Diesel V/s Hybrid V/s BEB’s Table1 shows the cost benefit analysis which compares theDiesel Conventional Buses V/s Hybrid diesel buses and BEB’s.The data has been collected from TfL statistics for bus andother articles related to bus transport in London. There is a fleet of 9549buses in London[4] (TFl, 2017) which comprises ofall the three variants included in the analysis. The assumption here made isuse of entire fleet as each type. From TfL report on Bus performance 16/17 itis found that on average bus travels 35600 miles a year. This data has beenmade a standard and remains the same for each variant throughout the analysis.The BEB considered here is the BYD double decker bus currently deployed on theroute 98. The bus packs a 100Kwh/hr battery pack which uses slow charging tocharge overnights at the Willesden bus depot and takes about 3-4 hrs to chargefully.[5] (Metroline,n.d.)The main aim was to find out the Overall operating cost of all thevehicles and compare them. As shown in the table the cost for the off-peak charging has beenassumed as 0.10p/kw, this charge can vary according to various boroughs anddifferent factors. On average bus travels 100 miles per day and price foroperation on each day is calculated as £4/day so which breaks down to 0.4p /mile.Now we also know that the BEB’s usually have replacement battery dueevery 6-7 years. But for this case the Buses provided by BYD has a warranty of12years which is almost the lifetime for a bus. So, no maintenance cost isconsidered in the analysis of costs for BEB’s. For BEB’s it can be consideredthat there will be a need for new infrastructure development which may cause arise in the overall cost for the BEB’s. As we don’t have any figure for thedevelopment of charging docks it is also not considered for the analysis. Thecharging dock once developed can be used by many buses at the same time andwould last for several years without any maintenance need. Figure 4 Cost comparison of all vehicles. Figure 5 Cost over Life span Following are the outcomes of the analysis:Ownership cost is almost double for BEB’s whencompared to Conventional diesel buses but when compared to hybrid dieselvehicle there is a very skew difference in their ownership costs. This islargely attributed to high price rate of battery packs used in BEB.Operating costs of the vehicles show largevariations as the cost for electricity is much low as compared to the cost ofdiesel. A single BEB can save up to approx. £42,000 which is almost the annualoperating cost of a diesel hybrid bus. This means if the whole fleet isconverted to BEB there can be tremendous savings on operational cost of publictransport buses. Diesel and hybrid diesel buses also show a considerabledifference but nowhere near BEB.Maintenance cost as shown in the table for BEBsare almost negligible as due to absence of mechanical spare parts the wear andtear would not happen. When talking about maintenance battery replacement costif any should be considered but in the considered case it is zero as themanufacturer has provide a warranty of 12 years for the battery pack provide inthe double decker bus. Totalcost per annum is the addition of ownership cost + operational costs which inthe initial years is high for the BEB. This due to large investment needed atthe time of procurement.The fig 5 shows the overall cost of operationover 12 years of life time, which shows that BEBs are highly efficient over thelong term. Even if the battery is to be changed it could be adjusted in thesame budget as for the hybrid diesel buses. The graph clearly suggest that itis extremely efficient to use BEB and can save around 350k over a life timewhen compared to a conventional diesel or hybrid diesel bus. For a whole fleetto be changed is somewhat hypothetical in near future but in his vision forbuses Mayor of London suggested to only uses BEB by latest 2037. This meansthere can be billions in savings overtime if the project is successfullycompleted.Apart from this the most important benefit wouldbe Zero-tailpipe emission from BEBs which can effectively and immediatelyimprove the urban air quality and in turn save millions of pounds spent onhealth care and other projects to eliminate the effect of greenhouse gases.More about this will be discussed in Environmental impacts of BEB’s.Thus, it can be said that currently the BEB’s are moreprofitable if they provide the needed range of usage and the cost benefitanalysis proves and supports the implementation of electric battery busesimmediately.Legislation and RegulationsWith advent of new technologies arrives the need to amend thelegislations already present or design new legislations and regulations. It isvery important that legislations for BEB’s are shaped at every level ofgovernance and implemented. Following are the policies that can be made atdifferent levels to incorporate and encourage the use of battery electricbatteries.International OrganisationsGreenhouse effect is a global problem and pollution causedanywhere would affect people everywhere, this should be kept in mind by eachorganisation. Emission of GHGs is a serious problem in big cities of everycountries. Now to reduce it most of the countries in UN should stay committedto save our planet earth from getting destroyed and there should be steps whichare mandatory for any member in a big organisation such as UN or EU. Anyviolations must be severely dealt with and provisions of sanctions or penaltiesmust be made, this is because air pollution is not only causing deaths tohumans who breathe toxic pollutants, but it also is posing a severe threat ifthe situations like now persists. Following are some important measures ordirectives which global organisation must lay out:Maximum permissible emission levels must be set out for eachcountry and no discriminations should be made between developing and adeveloped country. China accounts for 23% of global greenhouse emissions[6] (Worldatlas,2015)all over the world. Paris agreement COP 21 was signed by most of the world’s biggestcountries. US opted out of it as they would not be able to meet the levels setwhich should not be the case. Bigger economies must stand as an example and cutdown of GHGs. More and more deals must be made out on global level and theprogress on it must be reviewed time by time to ensure its successfulimplementation.National levelOnce the global agendas are set the countries on a national levelshould segregate different policies for different sectors which can be used byregulatory bodies and other industries and institutions to comply with thegoals set to meet the global agendas.For BEB’s England has been very proactive in the Europe andrecently became the world’s first to use a double decker BEB. China on theother hand has the largest market for BEB’s and has successfully managed toincorporate them in public transport in various cities. These countriespolicies can be set as an example for other countries. Following legislationscan be drawn from their policies:London has decided to only procure Hybridbuses or zero emission from 2018 and to only have zero emission buses by 2037. (TFl, 2017)Application of Ultra low Emission Zone(ULEZ)is done with dense traffic and higher Volume of COx and particulatematter in the air PM(2.5). (TFl, 2017)Buses that comply to the most stringent normsof Euro VI are only allowed on the streets. (TFl, 2017)For china the have provided bus manufactureswith attractive subsidies which has in turn made them the pioneer in theseindustries.Infrastructure development for BEB’s must besupported by government programmes.Efforts must be made, and more funds should beallocated for research in the technology of BEB’s. New ideas such as Solarcharging docks which makes use of renewable energy sources must be encouragedso that BEB’s leave minimum carbon footprint.IndustrialIt is important that the manufacturers keep in mind theemission levels and design the vehicles as per the norms.More Bus operators should try and incorporate BEB’s andfulfil their social responsibility.Consumer perceptionBEB’s have zero tailpipe emissions so they would not bethrowing black smoke right into urbanites faces. Diesel smoke is a bigcontributor to 6.5 million deaths a year due to air pollution. This shouldnotably mean that use of BEB’s virtually means no emission of greenhouse gasesor air pollutants. The electricity from power plants generated may still emitthose pollutants, but even if it is powered by coal plants, a BEB would averagefar less pollution per-mile than a diesel bus. Electric buses are much, much nicer experience- lower to theground, much more space (diesel engines take a lot of space), no diesel burningsmell & no noise.If the battery costs are brought down & with already lowoperational costs the total cost of running a bus can be brought to half thatof a diesel bus. These advantages when passed to community would mean lessmoney to travel on bus. BEBs can have positive social impacts as far as itsapplication is considered in urban areas. Air pollution and noise pollution inurban areas have been associated in a lot of studies across the globe. BEBs canalso end up reducing stress levels.Environmental ImpactsAir qualityAs we know currently most of the fleet of buses run onconventional diesel ICE engine. ICE engine is most popular but by burningfossil fuels this are the several side effects of diesel buses. Apart from thisuse of fossil fuels is at a peak & its price are also increasing day by daywith increase in demand.Figure 6 Oil demands The figure shows that we will shortly be running out of fossil fuels.The use of vehicles is increasing every year around theglobe and the demand is set to overcast the supply within next few years. BEBswill help ensure we have an alternative to run our buses.Air quality around the world has been in a grave conditionfor the past few years. BEBs are technology which will help us provide freedomfrom the emission which is caused by burning of fossil fuels. Dieselconventional buses use up to 100 times more diesel annually when compared to adiesel car. Currently the situation is so bad that a reputed daily guardianpublished an article which headlined- ‘Revealed- Every Londoner breathingdangerous level of toxic air particle.’ (Taylor, 2017) The articlehighlighted the seriousness of air quality problem that we are facing. Thearticle stated that almost 95% of the capital’s population live in the rea thatare exposed to high level of particulate matter in the air. [7]Figure 7 Particulate matter levels (Guardian) As the chart suggest the annual levels of PM2.5 are severelyhigh in and around the city of London. The situation is much worse when we thelevels are examined for central London. It is almost double the acceptablelimits suggested by WHO. BEBs when come into action will run through thestreets of the London but with zero tailpipe emission it is certain that thislevel will drop certainly and suddenly. This particulate matter can bedescribed as something as toxic a drop of tar which will go down directly tothe lungs and then to bloodstreams. This very fine particulate matter can be areason for strokes and heart attacks. (Taylor, 2017)The other major pollutant is Nitrogen oxides which is alsoproduced in our ambience, a pollutant which inflames the lungs, stunting theirgrowth & increasing the risk of respiratory diseases like asthma & lungcancer. London has one of the most acute problem across the world.[8] Figure 8 NO2 Levels London The figure shows how worse is the condition about nitrogendioxide in central London. It was reported that Putney High street managed tobreak its annual emission limits in just eight days in 2016. The areas ofKnightsbridge, Oxford street, Earl’s court & Brixton following the suitbefore the end of the first month. Government estimates 23000 people to diepre-maturely from nitrogen oxide pollution. (Taylor, 2017)PoliciesSeveral policies are designed to maximize the use of BEBs inLondon. Some policies have had a great impact in reducing the pollution fromthe city while some have not shown any effects.One such policy was to declare Ultra low emission zones inthe city where the vehicles meeting the highest standards are only allowed toenter. But if we consider the scale of the policy it only secures about 300,000citizens while ignoring the overall of 3 million which are affected by theatrocities of air pollution.The auto industry has for long tried and developed thevehicles which emit lowest NOx but have always failed. They have bylobbying tried to have their bread and butter secure by keeping on doing thewrong things to the environment. The norms have been manipulated and it is bestsaid that power is in money. The recently published EU limits have been anexample of this, Netherlands being the only country to oppose the limits. Thelimits are set such that it allows manufactures could design for up to doublethe acceptable limits by the WHO.[9](nelson, 2015)The powerful should understand that theneed is not to run from the problem but face it head on and take bolder steps.Technology of BEB must be accepted by European manufactures. 60 years ago,there was a ban on coal a similar ban is needed for diesel at least for urbanvehicles and specially for public transport.Dark sideThe BEBs run on electric and are zero-tailpipe emittingvehicles but are they greenest option available for transport in urban areas?Answer can be maybe no as the electricity used to charge the batteries of BEBscome from the burning of coal ion a thermal power plant. It can be made thegreenest if options are found to make it run on renewable sources of energy.Most of the electricity in UK comes from coal which is also a fuel which alsoproduces lots of carbon oxides and nitrogen oxides when combusted. Unless theelectricity coming to our grid is not by burning hydrocarbons there will be ahuge carbon footprint for any fully electric vehicle. But when a comparison isto be done burning a fuel in industry would be much more efficient that burningit on streets in different engines.Other hazard can be of battery disposal after its use. BEBsposses a large battery pack. Technology to recycle them must be developed sothat they don’t cause any hazard to environment. Most of the batteries arethrown away & are used as landfill in various areas, these will eventuallydegrade the soil & cause damage to vegetation also.  It is important thatBEB should be developed in such a way that they should be 100% green andenvironment friendly from well to wheel. This technology is developed as wedeveloped ICEs without assessing its impact on the environment. Cost might be abarrier but compromising now could mean serious consequences.BEBs can incorporate Other technologiesBuses in cities run over a fixed route and have a dedicatedlane in certain cities. A lot of research is put in developing an autonomouscar, the same technology can be used in buses with much lesser hindrance as itwould not have any other traffic on its way. Autonomous electric bus can takeout one of the largest cost that bus operators incur and that is labour cost.This can make bus travel highly safe and cheaper in future with much moreaccuracy to run on schedules.Apart from autonomous drive use of renewable sources can bedone to produce electricity for the charging of BEB at the charging docks. Useof solar energy to generate electricity and can be stored in storage cells andthen used to charge the batteries of the buses. This can cut down carbonfootprint to a very low level.  Suchtechnologies could make BEBs much more efficient and prove to be a game changerin the public transport sector.ConclusionThe idea of BEB has a clear future. It can prove to be thegame-changer to save the depleting air qualities in the cities and provide a boosttowards achieving a greener environment by cutting down the wasted fuel incongestion, providing more greener space & by removing the deadliest dieselICE in our cities.Implementing BEBs can not only be economically providing acountry with savings of hundreds of thousands of pounds on each bus but alsoserve good to its citizens health by saving them from life-threatening diseaseswhich could be rampant because of air pollution. There ought to be a lot ofchallenges along the path of revolution, but such has been the case with alltechnological revolutions, and they’ve been dealt with before and I am sureBEBs in near future will take over the market as the first choice for publictransport buses all over the globe.ReferencesAnon., n.d. Bus travel statistics, London:Department of transport.Bloomberg, n.d. s.l.:s.n.Independent, 2016.New double decker bus launch in london. march. Metroline, n.d. FirstZero emission Double decker, London: s.n.nelson, A., 2015. EUcaves in to auto industry pressure for weak emissions limits. Guardian.Taylor, M., 2017.Revealed: every Londoner breathing dangerous levels of toxic air particle. Guardian.tfl.gov.uk/corporate/publications-and-reports/bus-fleet-data-and-audits,n.d. Bus fleet data and audits, s.l.: s.n.TFl, L., 2017. TfLand the Mayor announce more fully electric buses, London: TfL.Wikipedia, 2017. Batteryelectric buses, s.l.: Wikipedia.Worldatlas, 2015. BiggestContributors to Air pollution, s.l.: s.n.YouGov, 2017. YouGovAir quality survey Results, London: s.n.[1]Data from Department of transport for bus travel.Source for history: Wikipedia Electric battery buses.[3] https://files.datapress.com/london/dataset/gla-poll-results/2017-01-26T18:50:00/YouGov%20Poll%20Air%20Quality%20Feb%202017.pdf[4] https://tfl.gov.uk/corporate/publications-and-reports/bus-fleet-data-and-audits[5] https://www.metroline.co.uk/blog/progress/world%E2%80%99s-first-zero-emission-electric-double-decker[6] https://www.worldatlas.com/articles/biggest-contributors-to-global-warming-in-the-world.html[7] https://www.theguardian.com/environment/2017/oct/04/revealed-every-londoner-breathing-dangerous-levels-of-toxic-air-particle[8] https://www.theguardian.com/environment/2016/feb/05/the-truth-about-londons-air-pollution[9] https://www.theguardian.com/environment/2015/oct/28/eu-emissions-limits-nox-car-manufacturersGet Help With Your EssayIf you need assistance with writing your essay, our professional essay writing service is here to help!Find out more