Chapter 13 Environment and Emissions
Chapter 13 Environment and Emissions
1 Introduction
1.1 This chapter provides information about the impact of transport on [certain aspects of] the environment with a focus on emissions and carbon. Statistics include atmospheric pollutants and emissions of greenhouse gases by types of transport as well as details of emissions levels of road vehicles. Data from other chapters within Scottish Transport Statistics are referred to in the analysis.
Key points
Transport accounts for a quarter of Scotland's greenhouse gas emissions under the definition set out in the Climate Change Scotland Act.
Road transport makes up 70% of transport emissions.
There were 878 Ultra Low Emission Vehicles registered in Scotland at the end of September 2013. Half of these were cars.
2 Main Points
Greenhouse gases
2.1 In 2011, Transport (including international aviation and shipping) accounted for 25.3% of net greenhouse gas emissions allocated to Scotland in the Greenhouse Gas Inventories. This is a 1.0% fall between 2010 and 2011. Total net emissions from all sources decreased by 9.9% between 2010 and 2011 before adjusting to take account of the EU Emissions Trading System. Within Transport's emissions, Road Transportation accounted for approximately 71% of the total, (Passenger Cars contribute 40% alone). Heavy Goods Vehicles and Light Duty Vehicles were the other significant contributors to Road Transportations emissions. International Aviation and Shipping contributed roughly 19% and Domestic Aviation 5% of transport's total emissions. Railways contributed roughly 1%. As these are estimates, using methodology designed to produce internationally-comparable estimates, apparent year-to-year fluctuations could be due in part to limitations in the underlying data. See Section 4.2 for details. (Table 13.2)
2.2 Chart 13.1 shows emissions over time by mode. Estimated car emissions have fallen by 13 per cent from a 2006 peak. Traffic levels have remained relatively stable over the last few years so the reduction in emissions will be largely due to the introduction of lower emission vehicles as well as other factors such as more fuel efficient driving. More detail on car emissions is in paragraph 2.7 of this chapter. Bus emissions have been increasing despite other data sources showing falls in vehicle kms on local buses. (Table 13.2)
2.3 More details on traffic volumes by mode can be found in chapter 5 of STS and details of personal modal choice can be found in chapter 11.
2.4 The Greenhouse Gas Inventories report the emissions of the six gases that are listed under the Kyoto Protocol.I In the case of Transport, the quantities of gases involved are relatively small except for carbon dioxide, which accounts for about 99% of all its emissions of greenhouse gases. (Table 13.3).
2.5 Comparisons with the UK are shown in Table 13.4. Scotland's emissions account for 8.1% of UK transport emissions. Looking at individual transport sectors, Road accounts for 8.5% of the UK total, rail 8.4% and maritime 14.0%, the latter due to allocation of oil traffic. Scotland's aviation emissions are only 4.6% of UK aviation emissions due to lower numbers of international flights. (Table 13.4)
2.6 Estimates of carbon dioxide emissions per passenger-km for different modes of transport are available only for GB/UK as a whole. The lowest emitting modes of transport per passenger-km are national coaches and national rail - 29 and 49 grams of CO2 respectively. Air travel tends to be the highest emitter per passenger-kilometre, particularly domestic flights, which account for 173 grams of CO2 per passenger kilometre. The basis of the estimates is described in section 4.3 (table 13.5).
Car emissions
2.7 Newly registered cars are becoming more efficient in terms of carbon dioxide emissions. Figure 13.2 shows the trend in average CO2 emissions for newly registered cars in Scotland. Average CO2 emissions in Scotland for new car registrations has fallen by 23% over the last ten years and by 4 per cent in the last year. (Table 13.6)
2.8 This pattern is shown in more detail in figure 13.3. If vehicles with unknown emissions are excluded (ie recalculating the percentages with unknowns removed from the total), the proportion of newly registered cars with emissions of 140g/km of lower has increased from 15 per cent in 2002 to 72 per cent in 2012. Cars with emissions of over 200g/km have decreased from 16 per cent of new cars to 2 per cent. These changes are at least in part the result of changes to vehicle excise duty bandings made by the UK Government in recent years. (Table 13.6)
Ultra low emission vehicles (ULEV)
2.9 The numbers of ultra low emission vehicles registered in Scotland have more than doubled since DfT began collecting the data in quarter 1 of 2010. Numbers have increased from 351 to 878 at the end of quarter 3 in 2013. The biggest increase has been in Plug-in-Grant Eligible cars which now account for 41 per cent of ULEVs and almost 90 per cent of newly registered ULEVs in the first three quarters of 2013. (Table 13.7 and 13.8)
Registrations by type of vehicle
2.10 The majority (99.5%) of vehicles licensed for use on the roads in Scotland are powered by either petrol or diesel. Historically petrol powered vehicles have outsold diesel but in 2011 diesel overtook petrol for the first time. The latest data shows that there were 104 thousand new diesel vehicles registered and 110 thousand new petrol vehicles registered in 2012 (74% of diesel vehicles were cars as were 95% of petrol vehicles newly registered. (Table 1.1 and 13.9 and 13.10)
2.11 Overall there is a gradual move to alternative fuel sources with 1 per cent of new registrations being powered by other means in 2012. 0.6% of new cars are hybrid electric and 0.1% of new car registrations are electric. (Table 13.9 and 13.10)
Air quality
2.12 The following paragraphs update the information published in previous versions of Scottish Transport Statistics. The data section of the "Air Quality in Scotland" website (see sources in section 4 of this chapter) provides detailed information on all sites while the publication section includes reports showing trends.
2.13At the selected monitoring sites, carbon monoxide concentrations were below the level of the air quality strategy objective (see section 3.1) in every year from 1998 to 2012. However, the annual mean nitrogen dioxide concentrations in the Glasgow Kerbside monitoring site exceeded the level set as an objective for December 2005 in every year from 1998 to 2012. Annual concentration in Inverness increased from 24 micrograms per cubic metre in 2010 to 30 micrograms per cubic metre in 2012, though still meets the annual mean objective. Levels in Dumfries have dropped from 40 micrograms per cubic metre in 2010 to 33 in 2012.
2.14 The air quality strategy objective for ground level ozone states that by the end of 2005 the maximum daily concentrations should not exceed 100 g/m3 on more than ten days per year. While ozone concentrations at the selected monitoring sites have fluctuated over the years, the target value was exceeded on more than ten days a year at the Strath Vaich site in most of the years from 1998 to 2009. In 2010 the target value was met at all of the sites except Peebles. However, in 2011 and 2012, Strath Vaich again failed this target. Since 1986, Eskdalemuir had not met the objective on 15 occasions, including 2009 but met it this year. Edinburgh St Leonards exceeded the target in 2004, 2005, 2006 and 2008 but has met it in every year since. In 2011, the objective was not met at Bush Estate, and Lerwick as well as Strath Vaich. Strath vaich was the only site to fail to meet the objective in 2012. Annual mean particulate concentrations in the four sites were below the December 2004 objective level (40g/m3) in all the years from 1998 to 2012 for which figures are available. The 2010 objective level (18g/m3) was met by all sites in 2011 and 2012, where data was available. Glasgow Centre failed the objective in 2010. (Table 13.1)
3. Notes and Definitions
Pollutants
3.1 The atmospheric pollutants listed in Table 13.1 have been selected because they are considered to be a threat to human health, and transport is understood to be a significant contributor to emissions of these pollutants. The Air Quality Strategy for England, Scotland, Wales and Northern Ireland contains air quality objectives for nine pollutants (benzene, carbon monoxide, lead, nitrogen dioxide, ozone, particulates (PM10), sulphur dioxide, 1,3-butadiene and polycyclic aromatic hydrocarbons (PAHs)). The objectives are policy targets expressed as a maximum ambient concentration to be achieved, either without exception or with a permitted number of exceedences, within a specified timescale. The table below sets out the agreed air quality objectives ( for the ones to which transport is understood to contribute significantly).
| Pollutant | Objective | Date to be achieved by | |
|---|---|---|---|
| Concentration | Measured as: | ||
| Benzene | 3.25µg/m3 | running annual mean | 31 Dec 2010 |
| Carbon monoxide | 10mg/m3 | running 8hr mean | 31 Dec 2003 |
| Lead | 0.5µg/m3 (500ng/m3) 0.25µg/m3 (250ng/m3) | annual mean annual mean | 31 Dec 2004 31 Dec 2008 |
| Nitrogen dioxide2 | 40µg/m3 200µg/m3 | annual mean hourly mean not to be exceeded more than 18 times a year | 31 Dec 2005 31 Dec 2005 |
| Particles (PM10)3 | 40µg/m3 50µg/m3 18µg/m3 50µg/m3 | annual mean 24-hour mean not to be exceeded more than 35 times a year annual mean 24-hour mean not to be exceeded more than 7 times a year | 31 Dec 2004 31 Dec 2004 31 Dec 2010 31 Dec 2010 |
| Ozone | 100µg/m3 | daily maximum (measured as an 8 hour running mean) not to be exceeded more than 10 times a year | 31 Dec 2005 |
Emissions.
CAT is the Carbon Account for Transport. The Carbon Account for Transport (CAT) fulfils a requirement of the National Transport Strategy to reduce emissions and to develop a carbon balance sheet for transport. It is published on a roughly annual cycle and contains:
Detailed analysis of officially reported transport emissions
Emissions efficiency estimates for passenger vehicles
Key forward looking transport indicators
Scottish transport infrastructure projects likely to have a significant impact upon emissions
RPP is the Reporting on Plans and Proposals. The Report on Proposals and Policies is a series of publications providing the most up to date and comprehensive analysis and assessment of the impact of a range of identified policies and proposals on Scottish emissions. The latest, the Second Report on Proposals and Policies (RPP2) was published in June 2013 and assessed the potential impact on emissions out to 2027.
Excluding IAS refers to the exclusion of International Aviation and Shipping in carbon emission calculations. The UK return to the UN on emissions does not include IAS as these are not within our gift to reduce. However, the UK Climate Change Act 2008 includes the option of adding an estimate of its share of global IAS emissions to the UK baseline (thereby making the reduction target harder) and the Climate Change Scotland Act 2009 includes it with certainty, estimates of these emissions are included in the publications as an additional, outside scope, annex. This allows there impact to be monitored for the two Acts.
Ultra Low Emission Vehicles (ULEV) - An ULEV emits extremely low levels of carbon dioxide (CO2) compared to conventional vehicles fuelled by petrol/diesel. They typically also have much lower or virtually nil emissions of air pollutants and lower noise levels. Since 2009, the Office for Low Emission Vehicles has considered ULEVs as new cars or vans that emit less than 75 grams of CO2 from the tailpipe per kilometre driven, based on the current European type approval test. Other definitions exist that suggest 50g CO2/km is a more appropriate threshold.
Plug in Grant - Since January 2011, UK motorists purchasing a qualifying ultra-low emission car have been able to receive a grant of 25% towards the cost of the vehicle, up to a maximum of £5,000. The Plug-in Car Grant has been designed to help make the whole-life costs of a qualifying car more comparable with petrol or diesel equivalents.
4.1 Pollutants and air quality objectives
4.1.1 The information on pollutants is taken from the Scottish Government online publication Scottish Environment Statistics Online. Some of the data are additionally published in the National Statistics publication Key Scottish Environment Statistics. Detailed information on all sites in the Scotland air Quality Database are available from the data section of the "Air Quality in Scotland" website (http://www.scottishairquality.co.uk). The air quality objectives are taken from The Air Quality Strategy for England, Scotland, Wales and Northern Ireland: Addendum.
4.2 Emissions of greenhouse gases by Transport allocated to Scotland
4.2.1 These figures are based on emissions estimates reported in Greenhouse Gas Inventories for England, Scotland, Wales and Northern Ireland: 1990-2011, compiled by Aether/Ricardo-AEA under contract to the Department for Energy and Climate Change, the Scottish Government, the Welsh Government and the Northern Ireland Department of Environment. In this inventory:
the figures are classified on the basis of the source of the emissions - so, for example, the Transport figures do not include a share of the emissions from the power stations that produce the electricity used by electric trains.
The figures given in the tables take account of removals of carbon dioxide as a result of Land Use, Land Use Change and Forestry (LULUCF). More detail can be found in the Carbon Account for Transport.
4.2.2 The way in which emissions are allocated to the different countries within the UK are described in the Greenhouse Gas Inventories report. In summary, the bases of the different estimates are:
- road transport - the estimated volume of traffic on the roads within each country. The estimates for carbon dioxide are constrained so that the total for the four countries agrees with the internationally-reported overall total for the UK as a whole (which was calculated from the total volume of fuel sold within the UK);
- railways - emissions from railway locomotives in Great Britain are disaggregated based on diesel oil consumption data for passenger services and National Atmospheric Emissions Inventory (NAEI) estimates for freight services. The data used in the 2006 inventory was reported for each railway company, whose area of operation can in most cases be allocated to one of the four constituent countries;
- civil aviation - estimates of emissions from domestic aviation are calculated based on aircraft movement data from the UK's major airports. The total number of domestic flights from each of the devolved administration areas has been calculated, and based on this, a fraction of the total UK emission has been allocated to each constituent country. This approach is also used to allocate emissions from aircraft support vehicles;
- national navigation - the disaggregation of emissions from navigation and coastal shipping has been derived in a similar way to the approach used for aviation, based on port movements in each constituent country;
4.2.3 Road Transport carbon dioxide (CO2) emissions are estimated using vehicle kilometre data constrained so the sum of the UK areas equate to the total for the UK inventory (where that total is derived from fuel sales data of petrol and DERV within the UK as specified in the reporting guidelines of the Intergovernmental Panel on Climate Change). A criticism of this method is that the presentation of results does not always provide a CO2 emission trend that is directly consistent with the vehicle kilometre trend data, as the fluctuations in UK fuel data have a more significant impact on the resultant emission trends. As an alternative, road transport CO2 emissions from the constituent countries of the UK may be estimated solely by vehicle kilometre data unconstrained to the UK total derived from fuel consumption data.
4.2.4 The difference in results between the constrained and unconstrained methods at Devolved Administration level largely reflects the difference in the results at UK level between bottom-up calculated fuel consumption using vehicle km data and fuel consumption factors and the fuel sales data in the Digest of UK Energy Statistics (DUKES). The reason for a disparity has previously been attributed to cross-border fuel sales ("fuel tourism") although model uncertainty was always emphasised as an additional, and probably a major explanation for the differences.
4.2.5 Any change in the methodologies or the factors used to calculate fuel consumption will affect the magnitude of the difference between calculated fuel consumption at national level and sales figures from DUKES and so, in turn, it will affect the disparity between the Devolved Administration CO2 emissions from the constrained and unconstrained approaches. Total carbon dioxide emissions from the vkm approach are 0.8% and 2.4% lower than the estimates constrained to DUKES for 1990 and 2011 respectively. The differences between the two approaches fluctuate year on year but they remain within 2.4% of difference for Scotland.
4.3 Carbon dioxide emissions per passenger-kilometre
4.3.1 The figures are taken from the new Greenhouse Gas Conversion Factor Repository created for Defra http://www.ukconversionfactorscarbonsmart.co.uk/
4.3.2 Figures are consistent with the factors used in the compilation of the UK's National Atmospheric Emissions Inventory (NAEI) and in the Greenhouse Gas Emissions Inventory compiled for Scotland and other constituent countries in the UK by Ricardo - AEA.
4.3.3 Figures are estimated using data for GB/UK as a whole and so do not relate specifically to Scotland. There are no estimates of emissions per passenger-kilometre for Scotland alone. The basis of the estimates is as follows:
- Road Transport - The factors used are estimated values for the average petrol and diesel car fleet travelling on average trips in the UK. This has been divided by an average car occupancy rate of 1.53 passengers to calculate average emissions per passenger kilometre.
- Rail - the national rail estimate refers to an average emission factor for diesel and electric trains. The light rail and tram factors are based on an average of the annual electricity consumption and passenger kilometre data provided by network operators, and a CO2 emission factor for electricity generation on the national grid from the UK Greenhouse Gas Inventory.
- Air - the emission factor is an aggregate representation of typical CO2 emissions from illustrative types of aircraft for the three types of air services - domestic, short haul and long haul. Broadly speaking the definition of domestic flights, are those within the UK, short-haul are those within Europe and long-haul are outside of Europe. In keeping with evidence from the IPCC, a 8% uplift factor has been applied to allow for sub-optimal routing and stacking at airports during periods of heavy congestion.
4.4 Vehicle Licensing data
4.4.1 Data used in tables 13.6 to 13.10 is provided by the Department for Transport Vehicle Licensing team. More information can be found in Chapter 1 of STS or on the DfT website.
5. Further Information
5.1 Pollutants - see Scottish Environment Statistics Online www.scotland.gov.uk/stats/envonline/menu0.asp or John Landrock of The Scottish Government, Environment Statistics branch (0131 244 0441).
5.2 Carbon dioxide and other greenhouse gases emissions allocated to Scotland - Martin Macfie of The Scottish Government, Environment Statistics (0131 244 7626).
5.3 Carbon dioxide emissions per passenger-kilometre is available from http://www.ukconversionfactorscarbonsmart.co.uk/
6. Other data sources
Within Scottish Transport Statistics:
Chapter 1 - Road vehicles
Chapter 5 - Road Traffic
Chapter 11 - Personal and Cross Modal Travel
Other Transport Scotland Statistics Publications:
Transport and Travel in Scotland - includes more detailed analysis of the SHS data, in particular:
Table 2 - Fuel costs
Table 7 - Mode of transport for travel to work
Table 11 - Car sharing
Table 18b - Car Access
Table 20 - Frequency of driving.
Table 28 - Frequency of train use
Scottish Household Survey Travel Diary - includes detailed tables using the Travel Diary dataset, in particular:
Table 2 - journeys by mode of transport
Table 2a - journey distance by mode of transport
Table 4a - mode of transport by journey distance
Table 5a - distance summary statistics by mode of transport
SHS Local Authority Results - provides breakdowns of SHS data by Local Authority, Regional Transport Partnership and Urban Rural Classification. In particular:
Table 1 - Travel to work by mode of transport
Table 2 - Travel to school by mode of transport
Table 16 - Journeys by mode of transport.
Department for Transport produce a number of related publications mostly at GB level, including:
Traffic estimates
Vehicle registrations.
DECC
Digest of UK Energy Statistics (DUKES)
Some non Official Statistics sources
Transport Scotland - Report on Proposals and Policies
Transport Scotland - Carbon Account for Transport
Figure 13.1 Atmospheric concentrations of selected pollutants recorded at urban and rural monitoring sites
Source: Scottish Government - Not National Statistics
1. The Aberdeen, Dumfries, Edinburgh Centre, Glasgow Centre, Glasgow Kerbside, Glasgow City Chambers, Grangemouth and Inverness sites are urban monitoring sites, and Eskdalemuir and Strath Vaich are rural sites.
2. Maximum annual eight hour running mean.
3. Annual average concentrations of atmospheric lead.
4. Annual mean concentration of atmospheric nitrogen dioxide.
5. Annual mean ground level ozone concentration.
6. Annual mean atmospheric PM10 concentration.
(*) Since 2003, results where data capture is less than 75% are not shown. Prior to 2003, a 50% data capture threshold is used.
(a) those to which transport is understood to contribute significantly - see text.
Source: Carbon Account for Transport (see sources section for more details) - Not National Statistics
1. From the Greenhouse Gas Inventories for England, Scotland, Wales and Northern Ireland: 1990 - 2011. Emissions are available annually only with effect from 1998. All the figures in this table have been updated to reflect changes to the methodology used. They are therefore not comparable with those previously published.
2. The method used to estimate carbon dioxide (CO2) emissions from road transport is based on vehicle kilometre travelled data constrained so that the sum of emissions across all parts of the UK equates to the total for the UK inventory where that total is derived from fuel sales data of petrol and DERV within the UK as specified in the reporting guidelines of the Intergovernmental Panel on Climate Change. Further detail can be found in Section 3.3 of the report and in Annex 2.
3. Includes emissions from fishing vessels, marine engines, personal watercraft, inland goods-carrying vehicles, motorboats and sail boats with auxiliary engines.
4. Net emissions take account of removals of carbon dioxide due to carbon sinks.
5. Includes LPG and road vehicle engines.
6. A split between International aviation and international shipping can be found in the Carbon Accout for Transport
Source: Scottish Government - Not National Statistics
1. The footnotes to Table 5.12 also apply to this table, including revision of the figures; though note that emisions of methane and nitrous oxide from road transport are estimated using vehicle kilometre data in both of the calculation methods, and the total emissions of these GHGs from the two methods are identical. There are no emissions of other greenhouse gases by Transport in the Inventory.
2. The figures for greenhouse gas emissions are expressed in terms of their Global Warming Potential in tonnes of carbon dioxide equivalent. To convert from tonnes of carbon dioxide equivalent to tonnes of other gases multiply by the following factors:
methane - 1/21, nitrous oxide - 1/310.
Source: Carbon Account for Transport (see sources section for more details) - Not National Statistics
1. Cars includes all LPG emissions and road vehicle engines (the 'passenger cars' and 'other' category in Table 13.2)
Source: DEFRA - Not National Statistics
1. Source: http://www.ukconversionfactorscarbonsmart.co.uk/ All figures are estimated using data for GB/UK as a whole so do not specifically relate to Scotland.
2. All Car figures assume an average car occupancy rate of 1.53 passengers based on the Scottish Household Survey Travel Diary: 2011
3. The long haul estimate is based on a flight length from the Guidelines of of 6482 km, short haul 1108km and domestic 463km.
4. In keeping with evidence from the IPCC, a 9% upflift factor has been applied to allow for sub-optimal routing and stacking at airports during periods of heavy congestion
Source: DVLA//DVADfT - GB figures published as DfT table VEH0256
1. The Department for Transport uses the term 'ultra-low emission vehicles' to refer to vehicles with significantly lower levels of tailpipe emissions than conventional vehicles. In practice, the term currently refers to electric, plug-in hybrid and hydrogen fuel-cell vehicles. For the purposes of this indicator, vehicles with fully electric powertrains, and cars with tail-pipe emissions below 75 g/km g/km of CO2 have been included at this stage.
Source: DVLA//DVADfT - Published as DfT table VEH0170
Notes & definitions (https://www.gov.uk/transport-statistics-notes-and-guidance-vehicle-licensing)
1. The Department for Transport uses the term 'ultra-low emission vehicles' to refer to vehicles with significantly lower levels of tailpipe emissions than conventional vehicles. In practice, the term currently refers to electric, plug-in hybrid and hydrogen fuel-cell vehicles. For the purposes of this indicator, vehicles with fully electric powertrains, and cars with tail-pipe emissions below 75 g/km g/km of CO2 have been included at this stage.
Source: DVLA//DVADfT - Published as DfT table VEH0130
~ denotes less than 50.
~ denotes less than 50.
