To what extent did the change to an over ground, metropolitan light-rail system in Manchester in 1992 influence an alteration in air quality.

Alex Reavley

UID: 8007436Supervised by Hugh CoeWord Count: 6324 words

This is a final year project for the BsC degree in Environmental Science, University of ManchesterAbstractThe issue of low air quality is one that poses a multitude of risks for the world. These risks can either be medical, biological and/or environmental. Transport produces huge levels of pollutants which cause these risks mostly through the emissions of motor vehicles. Light-rail trams create fewer pollutants per unit of distance travelled than any other means of motor transport such as petrol/diesel cars, buses and trains. Heavy-rail train lines in Manchester were refurbished in 1992 to create an over-ground, metropolitan light-rail system in an attempt to create a 'mass, reliable, quick means of transport from suburban areas to central business districts (CBDs). This, in theory, would drive a decrease in the pollutants emitted by the transport sector and therefore improve Manchester air quality. This research attempts to evaluate the extent to which this has occurred, whilst analysing other factors that have caused an effect on air quality. Another objective was to discover if the tram restoration had been an overall success in terms of patronage levels. Results showed that an average 45.3% decrease had occurred in carbon monoxide, nitrogen oxides, particulate matter and sulphur dioxide pollutants, excluding ozone. However, other factors were found to have initiated changes in air quality. For example, a change from a domination of petrol consumption to an overall increase in diesel use and an increase in the fuel economy and therefore engine efficiency of cars. Modal patronage changes of Manchester transport use showed notable decreases in bus travel to work and in some radial transport corridors, decrease in car use, whilst seeing large increases in overall patronage levels. Specific impacts of the tram refurbishment and other factors involved were hard to distinguish between. However it can be said with high confidence that the light-rail system has definitely made an impact and therefore has been a success and it is that success that is a good precursor to other tram systems being refurbished or built. Poor air quality is not an issue that is improving, actions are needed to diminish high levels of pollutants or face ongoing risks to health and the environment we live in.

Contents 1.0 Introduction (Page 3)2.0 Methodology2.1 Literature review2.2 Data collection and Sampling2.3 Data analysis3.0 Results3.1 Carbon monoxide (CO)3.2 Nitric acid (NO)3.3 Nitrogen dioxide (N20)3.4 Ozone (O3)3.5 Particulate matter (PM)3.6 Sulphur dioxide4.0 Discussion 4.1 Air quality4.2 Engine efficiency4.3 Changes in fuel type4.4 Traffic rates4.5 Modal patronage changes4.5.1 Metrolink phase 1 corridors4.5.2 Metrolink phase 2 corridors4.6 Effects of air pollutants5.0 Conclusion6.0 References7.0 AppendicesList of Figures/ TablesTable 1 (Page 3) Sources of specific pollutantsTable 2 (Page 4) Environmental ratings of different modes of transportFigure 1 (Page 5) Manchester Metrolink mapFigure 2-7 (Pages 8-11) Air quality data of pollutants (carbon monoxide, nitric acid, nitrogen dioxide, ozone, particulate matter, sulphur dioxide)Figure 8 (Page 13) Fuel economy of the USA Figure 9 (Page 15) Manchester road transport consumption typeFigure 10 (Page 16) Motor vehicle traffic in ManchesterFigure 11- 13 (Pages 18-19) Modal patronage of Manchester transport

1.0 IntroductionAir quality is the degree to which the air in a particular place is pollution-free (Oxford dictionaries). On average each person breathes in 14 cubic metres of air per day (EPA, 2012). If this air is high in pollution concentrations, it can have serious health impacts on many parts of the body, mainly the respiratory system. Low air quality is an issue of major concern, not only on a local scale but on a global level. Clean air is essential to maintaining the balance of life on the planet. High levels of air pollution can damage the environment, including man-made structures and also the biological system including wide ranges of ecosystems including wildlife, vegetation, water and soil (British Columbia air quality, 2013). Different specific pollutants originate from a range of sources and can cause different specific impacts to a multitude of various entities:Pollutant SourceEffects

Carbon monoxide (CO) Motor vehicle exhaust and the burning of materials such as coal, oil and/or wood Also released from industrial processes and waste incineration (EPA Victoria) Causes the disruption of oxygen delivery to all parts of the body.(DEFRA, 2013) Exposure can result in reduced work capacity, manual dexterity and reduce the ability to undertake complex tasks It can particularly impact people with cardiovascular disease(EPA, 2014)

Nitric oxide (NO)

Nitrogen Is the by-product of combustion of substances in the air as in fossil fuel plants and motor vehicles It is also formed naturally in reactions between NO2 and O3. (See equation 1)(Tucker, T. 2005)

Exposure irritates the path way of the lungs and can worsen respiratory diseases such as emphysema or bronchitis. This worsening can cause

Nitrogen dioxide (N2O)oxides (NOx) Natural sources produce 62% of total emissions. (See equation 1) Human sources produce the other 38% and come from motor vehicles, agriculture, fossil fuel combustion and industrial processes such as fertiliser production (What is your Impact?, 2006)increased hospital admissions and sometimes premature death.(EPA Victoria) NO2 gases are also known to contribute to environmental effects such as eutrophication and acid rain. (EPA, 2014)

Ozone (O3) Formed by various oxidation reactions with the nitrogen oxides gases and volatile organic carbons (VOCs) in sunlight. (See equation 1) (EPA Victoria) Not only impacts people with respiratory problems, such as asthmatics, but can severely reduce lung function causing chest pain, coughing and nausea.(EPA, 2014) Long term exposure can cause permanent structural damage to the lungs. Can also cause eye irritation(EPA Victoria)

Particulate MatterPM10 & PM2.5 Produced by both natural and anthropogenic activities(San Joaquin Valley APCD, 2012) PM10 (course particles) are formed by sources such as road dust, sea spray and construction PM2.5 (fine particles) are formed by sources such as internal combustion of engines and power plants. (Levy, J. 2007) High concentrations of PM can cause effects on heath such as lung and heart disease and also lung cancer. Children and elderly with existing respiratory problems are impacts greater by high PM levels and in some cases can cause premature death. PM can also cause environmental damage to man-made materials(EPA, 2014)

Sulphur dioxide (SO2) Emitted by the burning of coal, oil and/or gas in both power plants and motor vehicles Also produced by industrial processes such as chemical production (Levy, J. 2007) Exposure to high levels of SO2 causes negative effects on breathing systems and aggravation of existing respiratory illness. (EPA, 2014) It creates many of the same problems that NOx gases do.(DEFRA, 2013)

Table 1- The various sources and effects of different specific pollutants. Including carbon monoxide, nitric oxide, nitrogen dioxide, ozone, particulate matter and sulphur dioxide. Table 1 shows the specific sources and effects of each different pollutant measured in the research. The levels of these six pollutants will effectively show the level of air quality as a whole. As shown in table 1, motor vehicles create a huge proportion of emissions of air pollutants. Light-rail tram transport is an alternative option of transport that will reduce these emissions, whilst also creating a 'mass, reliable, quick means of transport from suburban areas to central business districts (CBDs). (Knowles, 1996) Mode of transportNOx (gpkm)PM (gpkm)Environmental rating

Train0.560.01420.7

Light-rail tram005.5

Bus0.270.007013.2

Diesel car0.20022.6

Petrol car0.017025.8

Motorcycle0.170.01329.8

Bicycle004.4

Walk005.4

Table 2- Different modes of transport with specific emissions for NOx gases and PM with also environmental ratings. See Appendices for full data for each mode. (Choppin, 2009)Table 2 shows the various modes of transport and their specific level of NOx and PM emissions with also environmental ratings where 0 is the lowest emissions impact. As you can see, light-rail trams have the lowest emissions and environmental rating out of all the motorised modes of transport compared to both diesel and petrol cars, trains and motorcycles. However, they are less environmentally friendly then both cycling and walking, although this is understandable.

NO + O3 NO2 +O2 and NO2 +hu +O2 NO + O3 Equation 1- The reactions that are the natural sources of NOx and O3 gases. (Where hu is UV light) (SOURCE)

Phase 3aPhase 1Phase 1The main determinants of the level of NOx and O3 gases in the atmosphere are two main reactions. These oxidation reactions create most of the pollutants that are in the atmosphere. These reactions cause a seasonal fluctuation of these gases which creates much higher levels of NO and O3 in the summer months and NO2 in the winter months. Phase 2

Figure 1- Manchester Metrolink system map. Shows phases 1, 2 & 3a. (Transport for Greater Manchester.) As shown in figure 1, Manchesters Metrolink phase 1 opened from Altringham to the city centre and on to Bury in April 1992. This consisted of a refurbishment of heavy-rail lines to create an over-ground, metropolitan light-rail system. Phase 2 was extended to Eccles through the redeveloped Salford docks in July 2000. Phase 3a was completed in February 2013 and runs along the Oldham and Rochdale line. Future extensions would see trams running to both Stockport and the Manchester airport from Didsbury and also to the Trafford Centre. Objectives of the research are to analyse the level to which the tram refurbishment in Manchester in 1992 has influenced the air quality of the city. It will take into account other factors that have initiated the changes found, whilst quantifying the level to which each have done so. The research will also look to discover if the Manchester Metrolink has been an overall success, through both overall and modal patronage changes. Limitations of the study will be the difficulties arising from effectively evaluating the impacts that each various factor has caused in casual effects of the air quality of Manchester and therefore seeing the actual impact the tram refurbishment has made. Poor air quality is a matter of grave concern because of the severe health risks it poses. With unprecedented increases in world population, established economies continue to develop, the threats of high air pollution continue to also rise. Light-rail tram transport systems are an effective way of creating a sustainable, environmentally friendly means of travel, whilst meeting economic and social needs of cities. As a result, an evaluation of the extent to which light-rail tram transport systems can affect low air quality is beneficial to many groups, not only to passengers of the trams and the population of Manchester but on a larger scale, through the governments deciding to construct them.

2.0 Methodology2.1 Literature reviewSecondary data was mostly collected through the Web of Science online search engine. This used the Web of Knowledge journal database and created results for peer-reviewed papers with valuable information on a range of topical subjects. The John Rylands University Library (JRUL) database was also used to locate results for different types of literature. Key words such as (Greater) Manchester, Metrolink, air pollution, air quality and trams were inputted into search engines in an attempt to find literature of use. The terms: environment(al), public transport, light-rail, transport impacts and United Kingdom (UK) were added to the keyword searches in an effort to find a wider scope of relevant results. The literature found, using these techniques, built up knowledge of the Metrolink scheme and informed of the changes it had undergone and caused to many sectors since its refurbishment in 1992.2.2 Data collection and samplingPrimary data was mostly recorded by the Department for Environment Food and Rural Affairs (DEFRA) and stored in the data archive. For the basis of this study, the Manchester Piccadilly monitoring site was used. The monitoring station is situated within a self contained air conditioned housing in the west-end of Manchester in a pedestrianised zone approximately 3 metres from the tram line. The surrounding area is generally open with commercial property (DEFRA monitoring networks). Selection options of the hourly network data archive were set accordingly; data type as measured data, monitoring site as Manchester Piccadilly, output type as to email address and the date range as the furthest records went back running to the present date. The six pollutants used in table 1 were inputted and then altered to create results for each. This was then downloaded from the email received, and inputted into Microsoft Office Excel to be analysed. This primary data recorded was the main body of the research and after analysis, made it possible to see the changes each pollutant had undergone since records began and therefore since the tram system was implemented. 2.3 Data analysisDue to the pollutants being measured at hourly intervals and the huge timescales they were measured on, it was necessary to take a daily average of the results to enable ease of use. However, doing so will lose notable changes in hourly fluctuations of air pollutant levels. These daily averages were comprised into one spreadsheet for each specific pollutant and plotted against the date they occurred. Trend-lines were plotted for the data on each graph and this aided the eye to see the overall changes that had occurred over the years. These take into account all data points recorded, and show the normal growth or decline behaviour that the data set has shown. 3.0 Results3.1 Carbon monoxide (CO)

Figure 2- Carbon monoxide readings from 1996-2007. Measured hourly at the Manchester Piccadilly site. Trend-line shows average change that occurred, with an extrapolation to the present day. (DEFRA Data Archive)Figure 2 shows the data recorded for carbon monoxide. There are large year to year seasonal fluctuations ranging from approximately 10 to 35gm-3. As shown by the trend-line, from 1996 to the end of 2007, the emissions of carbon monoxide have gone down by around 4.5gm-3 from 6.8 to 2.3gm-3. Limit values for exceedance of CO are not longer produced due to ambient concentrations found for many past years (Brookes et al. 2013)3.2 Nitric oxide (NO)

Figure 3- Nitric oxide readings from 1996-2014 (present day). Measured hourly at the Manchester Piccadilly site. Trend-line shows average change over the years. (DEFRA Data Archive)Figure 3 shows the readings of nitric oxide from 1996 to the present day. Again there are large seasonal fluctuations from year to year (see equation 1), in this case ranging from about 6 to 54gm-3. As shown by the trend-line the emissions have undergone a general decrease, but only to a small degree. Average emissions have decreased by about 1.2gm-3 from 4 to 2.8gm-3 in the years 1996 to 2014. 3.3 Nitrogen dioxide (NO2)

Figure 4- Nitrogen dioxide readings from 1996-2014 (present day). Measured hourly at the Manchester Piccadilly site. Trend-line shows average change over the years. (DEFRA Data Archive)Figure 4 shows the readings recorded for nitrogen dioxide to the present day from 1996. As figure 2 and 3 have shown there are seasonal fluctuations as the years go by (see equation 1). For nitrogen dioxide they range from 16 to 96gm-3. Again the trend-line shows the average decrease that has occurred since 1996 in both the maximum and minimum values seen. It shows an approximate 2gm-3 decrease from 11 to 9gm-3. Annual mean NO2 concentrations were set at 40gm-3, so exceedances were seen every year but the annual mean was within the limit value. (Brookes et al. 2013)

3.4 Ozone (O3)

Figure 5- Ozone readings from 1996-2014 (present day). Measured hourly at the Manchester Piccadilly site. Trend-line shows average change over the years. (DEFRA Data Archive)Figure 5 shows the ozone readings recorded from 1996-2014(present day). It also undergoes seasonal fluctuations (see equation 1), which are relatively uniform over the 18 years. However, the level to which they fluctuate varies from approximately 2 to 9gm-3. In this case the trend-line shows an average increase over the timescale, by about 0.5gm-3 from 3-3.5gm-3. No exceedances were made by O3 to above the 80gm-3 one hour limit value. (Brookes et al. 2013)

Figure 6- Particulate matter readings from 1996-2014 (present day). PM10 was recorded from 1996 to 2009 and PM2.5 from 2009-2014. Trend-lines for each show the average change of the data recorded over time. (DEFRA Data Archive)3.5 Particulate matter (PM)

Figure 6 shows the data recorded of both particulate matter 10 and 2.5 pollutants from 1996 to present day. Contrast to Figure 2-4, particulate matter readings do not fluctuate seasonally, but in a systematic pattern. However, there are evidently years with higher readings then others perhaps due to increased natural inputs such as sea spray or road dust. PM10 readings are approximately 2gm-3 higher than PM2.5 readings. Furthermore, according to the trend-lines only PM10 has decreased over the timescale. PM10 has decreased by approximately 1.7gm-3 from 4 to 2.4gm-3 in 1996 to 2009. PM2.5 has stayed approximately the same at around 1.5 gm-3 but in a much smaller timescale then PM10; 2009-2014. No exceedances were seen to rise above the PM10 limit value of an annual mean of 40gm-3. PM2.5 also did rise above the limit value annual mean of 25gm-3. (Brookes et al. 2013)3.6 Sulphur dioxide (SO2)

Figure 7- Sulphur dioxide readings from 1993 to 2014 (present day). Measured every 15 minutes at the Manchester Piccadilly site. The trend-line shows average change over the years. (DEFRA Data Archive)Figure 7 shows the data recorded for sulphur dioxide. This data shows us that no seasonal fluctuations occur. It also shows us there was a drop in levels of sulphur dioxide after 2004. However, there is a data gap for the first 10 months of 2005 this could have been because of a change in the instrument used to measure the data or an atmospheric effect. Overall, there has been a decrease in average levels of sulphur dioxide by 1.5gm-3 from approximately 2 to 0.5gm-3. No exceedances were observed to rise above the hourly mean of 350gm-3 or the 24-hour mean of 125gm-3 limit values. (Brookes et al. 2013)4.0 Discussion4.1 Air Quality Since the refurbishment of the tram system in Manchester in 1992, the air quality in the city has increased, apart from ozone levels. Trams create less pollution than any other means of transport, including both petrol and diesel cars, buses, trains and motorcycles (See table 2). So it is evident that an increase in the use of trams as an alternative to other means of transport would decrease the air pollution created. In figures 2- 6 you can see clearly that this decrease in air pollution has not only occurred, but also that the level varies between each specific pollutant. Carbon monoxide decreased by approximately 66% in 1996-2007. Nitric oxide decreased by approximately 35% in the years 1996-2014. Nitrogen dioxide decreased by a lesser degree of approximately 18% in the same 18 year time frame. These decreases in NO and NO2 are likely caused by a decrease in emissions created by industrial sources. The large decrease in NOx emissions is encouraging, the World Health Organisation (WHO) set air quality guidelines for NO2 as an annual mean of 30gm-3 and 200gm-3 as the 1 hour mean for the whole of Europe (WHO, 2005).This as a result means Manchester air pollution is well below those guidelines for the Piccadilly site. However, a much more detailed analysis of NO2 levels using many other data locations including background sites is necessary to make this claim viable. All air pollutant levels have not decreased in the years 1996-2014. Ozone levels in Manchester increased by approximately 17% since 1996. Ozone is produced when nitrogen oxide gases react with volatile organic compounds (VOCs). (See equation 1 on page 1). Although, even after this increase in ozone levels the emissions are still below the 180gm-3 1-hour mean guideline set by the WHO for Europe (WHO, 2005). Only one type of particulate matter (PM10) decreased over the years, PM10 decreased by about 43% from 1996-2009 and PM2.5 stayed at roughly the same level from 2009-2014. Lastly sulphur dioxide saw an overall 75% decrease in the years 1996-2014. This massive decrease is likely caused by the huge reduction and limitation or restriction of use of fossil fuels with high sulphur content. These decreases have caused the levels of SO2 to be much lower than the 20gm-3 annual mean and 350gm-3 1-hour mean guidelines set by the WHO for Europe (WHO, 2005).Nevertheless, it is very difficult to distinguish between the factors that have driven this decrease to occur. The refurbishment of the heavy rail lines to a light rail system has definitely been one of a combination of factors in influencing this decrease, however the level of which, is one to be disputed. Other factors have also played their part; such as changes in engine efficiency, alterations in use of fuel types, and variations in traffic rates. In an attempt to quantify the level at which Metrolink has decreased the air quality in Manchester, the specific changes of the other factors involved were analysed. 4.2 Engine efficiencyThe production of pollution of an engine is directly related to the efficiency of said engine. An engine with a low efficiency will use more fuel per unit of distance and therefore create more harmful emissions both directly and indirectly. Pollutants such as PM2.5, NO, NO2 and CO are all produced by internal combustion engines (see table 1). If the efficiency of these engines is low, then a higher level of these pollutants will be produced from one unit of fuel. As the prices of oil and gas rise and the issue of air pollution continues to rise in both local and government awareness, car manufacturers are constantly trying to improve engine efficiency. The quality of a highly efficient car is now a huge selling point for these manufacturers as the consumer wants to be able to save money and many also want to play their part in the fight against air pollution for personal or more widespread reasons. Energy efficiency is measured by the distance per vehicle per fuel volume. Worldwide cars are getting more efficient and more powerful. The United States of America is a good example to use to show this increase in efficiency because it produces such a high volume of cars and is the worlds leading economy.

Figure 8- Adjusted fuel economy for the United States of America (USA) in 1993-2013. With guidelines set for average fuel economy level by 2017 & 2025. (EPA, 2013)Figure 8 shows the average adjusted fuel economy for the US cars sold in the years 1993 to 2013 (present day). In the first 12 years of data recorded, fuel economy decreased by around 1 MPG. This decrease was coupled with increases in vehicle weight and vehicle power (horsepower). Then since 2005 to the present day, technological innovations have driven an increase in fuel economy and therefore energy efficiency, whilst still seeing an increase in vehicle power but a steadying of vehicle weight. However, this data is only for the USA and the state of the transport sector in the UK is different. Similar data for the UK fuel economy is difficult to find. Although, many of the cars included in these predictions will also be sold and used in the UK, such as Mazda, Honda, Toyota, Volkswagen, Subaru, Nissan, BMW and Ford. These figures also only take into account new cars sold and dont include older cars fuel economies. Guidelines have been set for the future fuel economy of the United States, at 36.6 MPG by 2017 and 54.5 by 2025. This is an attempt to drive increases in economic development and as a result, use of electric cars and also to increase the pressure on the mass- manufacturers to produce more fuel efficient cars through technological innovations (Vlasic, 2012).So, fuel economy and therefore engine efficiency in the USA is increasing, and looks likely to continue to dramatically increase over the next decade. As these increases occur, less and less fuel is used per unit of distance travelled. This means less and less air pollution is emitted per unit of distance travelled. So, assuming the state of the transport sector in the UK is relatively similar apart from differences in diesel consumption, these increases in engine efficiency will have contributed to the relative reduction in level of some of the pollutants, namely CO, PM2.5, NO and NO2. In the US, no diesel is used in motor vehicles so therefore there are differences in emissions produced and therefore makes it harder to make conclusions about the how the Manchester fuel economy has changed. However, a study undertaken by the International Council on Clean Transportation (ICCT) showed that there were about 21% differences between the fuel consumption quoted by the car manufacturers and the actual real-world figure. These disparities are due to variations in driving style, road, traffic and weather conditions. There was always knowledge of these differences between the real and the claimed efficiencies; however it is thought that this gap is widening (AA, 2013). Analysing the nature of this widening gap to use in engine efficiency statistics would be beneficial to future research. So, to sum up, it is not clear whether the increase has made the impact on air quality possible with the increases in fuel economy, however it will have definitely driven a slight effect.

4.3 Changes in fuel typeDiesel and petrol fuels create different types and levels of emissions. Petrol is less fuel efficient then diesel as it has less energy per litre. However, the emissions have been reduced hugely by the introduction of catalytic converters. They oxidise pollutants such as CO to form carbon dioxide (CO2) and reduce the level of NOx emitted. As a result of these conversions, the car uses more fuel and therefore is less efficient. Petrol cars emit more CO than diesel cars, but produce less PM and NOx pollutants. Diesel fuel contains more energy per litre, this tied with more efficient diesel engines makes running a diesel car much more efficient in general. Although, a Diesel car compared to a petrol car fitted with a catalytic converter produce more NOx and PM emissions. Nevertheless in general diesel cars are considered to be cleaner than petrol cars due to the efficiency differences and lower maintenance requirements (Air Quality, 2013). As changes in consumer choices and the issue of air quality awareness increases occur, there has been a change in the use of both petrol and diesel cars.

Figure 9- Manchester road transport fuel consumption type from 2002-2011. Including petrol/diesel cars, buses and motorcycles. (Department for Energy and Climate Change, 2013)Figure 9 shows the change in fuel consumption type for the road transport in Manchester from the years 2002-2011. The road transport fuel consumption in total has seen a 15% decrease. Since 2002 diesel cars have increased by approximately 53%. This has occurred at the same time as petrol cars have decreased by about 36%. Ratios between diesel and petrol have changed from approximately 1:6 in 2002 to approximately 1:2 in 2011. Buses have also decreased by about 29% since 2002. However, this decrease in fuel consumption may be caused by an increase in the number of hybrid-engine buses and not a decrease in the total bus fleet. These hybrid-engine bus rapid transport (BRT) vehicles produce less PM but more NOx emissions (Hodgson et al. 2013) .Taking into account the overall decrease in road transport fuel consumption in Manchester, it is evident that the use of diesel cars has increased massively and the use of petrol cars has decreased massively. This theoretically would mean decreases in the emissions of CO but increases in the emissions of PM and NOx pollutants. This change has gone along with the efficiencies of diesel engines and clean up technologies increasing at the same time. In figure 2, we have seen decreases in the level of CO being produced; however the timescales of figure 2 and figure 9 do not massively overlap. There was no increases in PM (figure 6) and NOx gases (figure 3/4), but this is likely to be offset by other factors involved, one of which is the refurbishment of the trams driving a reduction in the emissions produced through that sector. Although, a limitation of the data used for changes in consumption of fuel types is that the timescale is not extensive enough and doesnt run to the present day (Air Quality, 2013).4.4 Traffic rates

Figure 10- Motor vehicle traffic in Manchester for the years 1993-2012. (Department for Transport, 2012)It is obvious to say that higher traffic rates will mean high emission levels. This is due to more cars being on the road producing more emissions. Decentralisation of workers from the central business district (CBD) to the suburbia areas has partly caused an increase in traffic rates in many cities around the world. Ever unprecedented increases in populations also cause an increase in traffic rates. Greater Manchester has seen large growth in population in the last 13 years. Rising by approximately 2.7% from 2.48 million to 2.55 million since 2001 to 2011 and is predicted to rise a further 15.7% to 2.95 million by 2031 with 36% of this growth being seen in the city alone. (Kirby, 2013) These increases in population will almost certainly cause increases in the traffic rates of the city. As shown in figure 10, in the years 1993 to 2012 there has been an overall increase in traffic rates of approximately 6%. However, this 6% increase equates to an extra 86 million miles being driven on the roads. With the increases in population being seen in Greater Manchester, a higher increase in the traffic rates would have been expected. Comparing the UK as a whole over the same timescale, their traffic rates have increased by 18% respectively. This associates to an increase in the motor vehicle miles by 46,426 million respectively (Department for Transport, 2012). So, contrary to most of the results found previous, traffic rates increasing would cause a decrease in air pollution. However, Manchester being Britains Boom-City (Kirby, 2013), seeing large rates of population growth, you would expect to see large rates of traffic rate growth. The refurbishment of the tram system in 1992 is one of a combination of factors that have limited these increases in motor vehicle traffic.To sum up, in general the air quality in Manchester has decreased since 1993 to a moderate level with the exception of ozone emissions increasing. Due to the specific levels of emissions produced by trams, and the fact that they are lower than all other forms of transport (see table 2), we can safely say that the tram refurbishment has been one of a multitude of factors that have driven this decrease. However, the complexity of the air quality system means it is difficult to make confident claims about the nature of the decrease without including other factors. These other factors, such as changes in engine efficiency, alterations in use of fuel types, and variations in traffic rates, have caused varying influences on the various different pollutants. Furthermore, to enable it possible to say with a higher confidence that the tram restoration has made a large effect on the air quality we have to analyse changes in the modal patronage of different transport types in Manchester since 1992. 4.5 Modal patronage changesSince the trams were refurbished in 1992, changes have occurred in the transport people use. These changes are driven by alterations to prices, availability, location and aesthetics of different types of transport. As the economic system works, supply and demand levels are linked together. For example, a member of the general public may demand a cheaper alternative to the train line built near their house to enable fast and economically viable travel to and from the city centre. However, the supply only provides the irregular, slow, expensive option of the train, therefore it becomes more economically and aesthically viable to take the bus instead. The tram system being restored created an alternative means of transport available to the general public. As mentioned before, this mode of transport creates less air pollution then most of the others, including train, bus, motorcycle, car driver and passenger, but more than walking, cycling and working at home. Thus, analysis of the changes in the patronage of different means of transport would be beneficial in discovering the true specific impact the tram refurbishment had on Manchester air quality. To do this, statistics taken from census data was analysed.

Figure 11- Patronages of different modal transport in the Metrolink phase 1 corridor. Travelling to All Destinations of work. In the years 1991 to 2001. Including light-rail tram, car driver, car passenger, train, bus, walk, motorcycle, bicycle, other and works at home. Other includes the Census categories other and not stated in 1991 and other and taxi in 2001. (Lee et al. 2013) 4.5.1 Metrolink phase 1 corridorsFigure 11 shows the changes in patronages to all destinations of work of the nine means of transport mentioned earlier from 1991-2001. After Metrolink was created in 1992, by 2001 6% of all destinations were taken on the light-rail tram. Bus use dropped by 4% and car driver/ passenger transport increased by 1%. Members of the public working at home increased by 4% but people walking dropped by 2%. Accompanied with the increase in tram use, the decrease in bus use and increase in people working at home would be one of the factors resulting in an increase in the air quality. However, these modal patronage changes are only relative and the absolute changes in displacement of miles travelled in other means of transport needs to be analysed to estimate levels of emissions offset. The other factors involved are the increases in motor vehicle engines and emission clean up technologies. However, the slight increase in car use, both drivers and passengers, would have counteracted this decrease.

Figure 12- Patronages of different modal transport in the Metrolink phase 1 corridor. Travelling to City Centre destinations of work. In the years 1991 to 2001. Including light-rail tram, car driver, car passenger, train, bus, walk, motorcycle, bicycle, other and works at home. Other includes the Census categories other and not stated in 1991 and other and taxi in 2001. (Lee et al. 2013) Figure 12 shows the changes in patronage of means of transport with city centre destinations for work over the timescale 1991-2001. In the 10 years and after the tram system was refurbished, light rail trams took over quarter of the passengers with city centre work destinations %. This increase was mostly at the cost of a decrease in train use, dropping by 19%. Car driver/ passenger transport also decreased by 4% and bus use decreased by 7%. All these changes would have partly contributed to a increase in the air quality with the light-rail tram being the least emitting form of transport. 4.5.2 Metrolink phase 2 corridors

Figure 13- Patronages of different modal transport in the Metrolink phase 2 corridor. Travelling to All Destinations of work. In the years 1991 to 2001. Including light-rail tram, car driver, car passenger, train, bus, walk, motorcycle, bicycle, other and works at home. Other includes the Census categories other and not stated in 1991 and other and taxi in 2001. (Lee et al. 2013)Figure 13 shows the changes in patronage of means of transport over the years 1991-2001 with all destinations of work. By 2001, light-rail trams had made up 3% of the transport used travelling to work. This was accompanied by a decrease in 7% of bus use and an increase of 3% in car users, whilst the use of the train stayed the same at 1%. People walking reduced by 2% but members of the public working at home increased by 4%. These changes would have caused a slight decrease in the air quality due to the decrease in bus use and increase of workers at home, but only slight due to the increase in the number of car drivers/ passengers.

Figure 14- Patronages of different modal transport in the Metrolink phase 2 corridor. Travelling to City Centre destinations of work. In the years 1991 to 2001. Including light-rail tram, car driver, car passenger, train, bus, walk, motorcycle, bicycle, other and works at home. Other includes the Census categories other and not stated in 1991 and other and taxi in 2001. (Lee et al. 2013)Figure 14 shows the changes in modal transport patronage for city centre work destinations in 1991-2001. In the timescale, light-rail trams amount to 14% of the transport used. The total of car drivers and passengers decreased by 6%, bus use decreased by 9%, and users of trains decreased by 2%. These decreased were coupled with an increase in people walking of 3%. These decreases in the will have caused the air quality to increase as all create more emissions then light-rail trams. To sum up, the tram refurbishment is one of the factors that has evidently caused a relative shift in modal patronages of transport with seen increases in total partronage of the Manchester Metrolink. However, the overall changes in levels of various modes of transport would have to be analysed to be able to quantify the level to which this has occurred. In phase 1 corridors, passengers with all destinations of work have decided to use the light-rail tram instead of the train or bus. In the same corridors, workers with city centre destinations have massively started to use the tram in the expence of both train and bus use. In phase 2 corridors, members of the public with all destinations have decreased use of mostly bus use. People with city centre work destinations in the same corridors have used the bus and car less. The aim of the tram refurbishment was to cause a shift away from car use to reduce traffic levels instead of bus use. In general, over both corridors, more people have also started to work at home. This shift might be linked with the increase in availablity and quality of the internet making it possible to do so. So, it looks like the increase in light-rail tram patronages has come from a shift away from bus travel to work. Knowles, 2007 found that the Manchester Metrolink had saved over 5.6 million in total and 2.5 million car journeys per year. These specific changes will cause the specific air quality to increase in Manchester due to the lower emissions trams produce compared to cars (table 2). Furthermore, the census data used in figures 11-14 only covers 8 years of the phase one and 5 years of the phase 2 Metrolink schemes. Therefore, a more extensive data set covering more years of modal patronages would be useful. Furthermore, total patronage in 2001 was 17.2 million, which has now risen to 25 million in 2013. (Lee, 2013) So, it would be beneficial in future research to see how the modal patronages changed with the extra increase of 7.8 million passengers.

5.0 ConclusionIn conclusion, the air quality of all 6 pollutants in Manchester, carbon monoxide, nitric acid, nitrogen dioxide, ozone, particulate matter and sulphur dioxide, since 1996 have increased on average by 47%, excluding ozone. Since the tram refurbishment in 1992, we can say with high confidence that this restoration has been one of a multitude of factors contributing to this increase with the displacement of car journeys and the increased Metrolink patronages coming from changes in the mode of transport used away from higher emitting types. Aspects such as changes in fuel type and engine efficiency have also driven this air quality increase. Type of fuel consumption is shifting from a domination of petrol, to more and more diesel use and as a result producing less of most specific pollutants. Engine efficiency is increasing to unprecedented levels as fuel economy increases, reducing the level of emissions produced per distance travelled. However, increases in Manchester traffic rates have counteracted the increase in air quality. But these changes have been limited and were lower than expected with population increases so therefore have made restricted impact on the air quality.Limitations of the work undertaken would be a lack of different location sites for the analysis of air quality. Ideally, more than one site would have been used such as a background site or a site outside the city centre but still in the vicinity of the tram lines. This would have increased overall accuracy of the results and cut out more anomalies. Additionally, using more specific data could have been used in an attempt to make overall conclusions found more precise. For example, for engine efficiency, data that was specific to the UK instead of the US would have been beneficial. For both changes in air pollutant levels, fuel type and modal patronage changes, it would have been constructive to use data from 1992 to the present day. However, limited accessibility and availability of statistics limited this.Through conducting this research, it could be concluded that the change to an over ground, metropolitan, light-rail system in Manchester has been a huge success in both increasing the air quality of the city and also in specific targets set, i.e. providing fast public transport access to the Manchester people. Essential to solving the huge global issue that is low air quality or high air pollution is making our transport cleaner and more environmentally friendly. It varies across the world, but it is thought that between 50 and 90% of urban air pollution is created by motor vehicles in the US (Smith, 2010). As demonstrated in this work, the light-rail tram is a effective and efficient way in reducing that air pollution created by transport by giving the public another attractive option of travel that is a much lower emitter of air pollutants (see table 2). This aspect, as well as other social and economic factors, is the reason many cities are proposing, planning or under construction of these light-rail tram systems, such as Leeds, Edinburgh, Liverpool and London (Trams in the UK, 2007). However, as successful as the Metrolink scheme has been, poor air quality is still a major concern on a worldwide scale. Outdoor air pollution caused 3.7 million premature deaths worldwide in 2012. Although, 88% of these were in low to middle income countries, the influence of low air quality is still paramount, not only at a local, but at a global level (WHO, 2014). The need for both individuals and for governments to address the issue is essential, or risks of a continuation of health problems and premature deaths will be ongoing. As said by the World Health Organisation clean air is considered to be a basic requirement of human health and well-being. However, air pollution continues to pose a significant threat to health (WHO, 2005)

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7.0 AppendicesIDDetailOccupancyCO2 (gpkm)NOx (gpkm)Pms (gpkm)Env.Rating

RAILInterCity 125: diesel-electric (national network)75% occupancy41.96890.5563020.01433920.68

LIGHT-RAIL TRAMInterCity 225: electric (national network)75% occupancy0005.53

BUSDiesel (from 2006): Urban use75% occupancy33.91640.1802280.00167310.05

BUSDiesel (2001-2006): Urban use75% occupancy33.91640.2536120.0080988613.49

BUSDiesel (1996-2001): Urban use75% occupancy33.91640.36730.011254815.93

BUSDiesel (comprised 1996-2009): Urban use75% occupancy33.91640.26704670.0070088913.16

CARAverage city-car dieselAverage occupancy (1.6 passengers)83.43030.202019022.62

CARAverage city-car petrolAverage occupancy (1.6 passengers)95.79070.0173424025.81

MOTORCYCLE2-Stroke