Carbon Account for Transport
Chapter 2: Historical emissions analysis
2.1 Background and data sources
The emissions data presented in this chapter are from the 'Greenhouse Gas Inventory for England, Scotland, Wales and Northern Ireland: 1990-2013' (GHGI) unless otherwise stated. The GHGI is compiled on an annual basis and the complete time series of all greenhouse gases is updated in each publication to take account of improved data and any advances in calculation methodology. This updating has led to a significant increase in the base year Scottish emissions figure for 1990 which in turn has impacted on the absolute emissions reduction required to meet the key climate change targets. The greenhouse gases associated with transport and recorded by GHGI are Carbon Dioxide (CO2), Nitrous Oxide (N2O) and Methane (CH4).
The transport category within the GHGI covers emissions from road, aviation, rail and maritime transport. While domestic aviation and shipping emissions are recorded in the GHGI, emissions associated with international aviation and shipping (IAS) were not originally reported. However, using existing data sources, an indicative assessment of the emissions from international aviation and shipping from each country in the United Kingdom was first published in 2009 and continues to be published within the dataset that accompanies the GHGI publication. Consequently, in line with the Scottish Government commitment to include emissions from IAS within the targets set by the Climate Change (Scotland) Act, references to aviation and maritime emissions in this document refer to both domestic and international, unless otherwise stated.
In line with the methodology used to report against the Climate Change (Scotland) Act, the transport emissions reported in this section only cover emissions at the point of use (tailpipe emissions). Consequently, no lifecycle impacts within the transport infrastructure and no displaced impacts, such as the emissions generated by the electricity used on electrified railways, are included.
2.2. Total emissions trends for Scotland and the Scottish transport sector
In 2013 total Scottish emissions from all sectors amounted to 53.0 mega-tonnes of carbon dioxide equivalent (MtCO2e). This total represents a 2.0 MtCO2e or 3.6% reduction from the equivalent 2012 figure. Compared to the 1990 base year Scotland has reduced its total emissions by 34.4%.
Transport's share of this Scottish total is 12.9 MtCO2e. After a sequence of almost continual increases in transport emissions from 2000, the run peaked in 2007. Since reaching this peak of 14.8 MtCO2e transport emissions have fallen year on year and are now below their 1990 base year level of 13.2 MtCO2e and 13%, or 1.9 MtCO2e, below the 2007 peak.
The run in emissions reductions has been as a result of a number of factors. Principal among them initially was the continuing uneven nature of the recovery in real household incomes, a growing investment in public transport infrastructure, improvements in fuel efficiency, government emissions policies, land-use planning and high global oil prices. More recently, as road emissions have stabilised it is lower maritime emissions that are behind the continuing downward trend.
The latest data on economic performance in Scotland shows 11 quarters of positive GDP growth. The close correlation between GDP and transport emissions will continue to put pressure on the downward sequence of emissions.
With IAS emissions excluded, the transport sector accounts for 20.8% of total Scottish emissions: with them included the proportion rises to 24.4%. The respective shares in 2007 and 1990 were 18.7% and 22.3%, and 13.6% and 16.3%. Figure 1 shows the growing relative importance of transport emissions in Scotland's emissions total.
Source: Greenhouse Gas Inventory, NAEI, 2015, Transport Scotland. Total emissions calculation excludes the impact of the EU Emissions Trading System.
2.3 Emissions analysis by transport sector
2.3.1 Road Transport
Road transport emissions include all private, public and commercial road vehicles. In total, this category accounts for 9.3 MtCO2e or 72.0% of total transport emissions. The 2013 figure is marginally (less than 0.1MtCO2e) lower than the 2012 figure because the fall in car emissions just exceeded the rise in LGV and bus emissions.
Figure 2 shows that road emission rose almost continuously from 1990 to a peak in 2007 of 10.2 MtCO2e. Since this 2007 peak, road emissions have fallen for five out of the last six years and in 2013 stand 9% below this peak. Total road kilometres since 2007 are only down 2%. Road emissions are though still 2.5% above the 1990 equivalent figure.
Figure 3 shows the growing relative importance of goods vehicle emissions over cars. While the share of road emissions from cars has fallen from 63.6% to 54.4%, total goods vehicle emissions have risen from 31.8% to 39.4%. Bus and coach emissions have also seen a very small increase over the period but emissions from buses still amount to less than 6% of road transport emissions.
As well as reflecting improvements in car energy efficiency, car emissions have been affected by changes in the make-up of the passenger car fleet by fuel type. With diesel engines being more fuel efficient than their petrol equivalent (all other things being equal) the balance of the fleet moving in favour of diesel (see Figure 4) has improved the GHG emissions situation. Should the split in new registrations between diesel and petrol settle (around a 50:50 split) this year on year reduction in fleet emissions as a whole from the switching to diesel will end. Further detailed analysis of road transport emissions by vehicle type and road type is undertaken in sections 2.4 and 2.5.
2.3.2 Maritime Transport
Emissions from maritime transport in 2013 are estimated to be 1.6 MtCO2e or 12% of total transport emissions. Figure 5 shows that emissions from this sector have been volatile, due in part to methodological and GHG reporting changes.
Maritime emissions fell by over one million tonnes from their 1998 peak of 2.8 MtCO2e to 1.7 MtCO2e in 2002. Thereafter they rose by 0.6 MtCO2e to reach 2.4 MtCO2e in 2008 before falling to a new series low in 2013. The 2013 estimate is 39% or 1.0 MtCO2e below the equivalent 1990 figure. The volatility in the series can be attributed to the performance of international shipping sector (IS) as historically IS emissions account for more than 70% of all maritime emissions. Figure 6 also shows domestic maritime emissions are on a gentle downward pathway.
In 2013 aviation emissions rose back to their 2011 level of 1.9 MtCO2e. This represents an increase of less than 0.1 MtCO2e over 2012 but aviation emissions are some 0.5 MtCO2e or a third above their 1990 base year. Aviation emissions now represent 14% of total transport emissions. Figure 7 shows the increasing trend in emissions from 1990 out to 2007 (2.3 MtCO2e) before the recent recession lead to lower year on year emissions until 2010.
Figure 8 shows that from 1998 to 2004 emissions from domestic and international aviation were very similar and moved together. Since then the series have diverged. In 2013 international aviation emissions are estimated to account for 60% of total Scottish aviation emissions, almost the opposite of the situation in 1990 when domestic aviation emissions accounted for 61% of aviation's total. Between 2012 and 2013 domestic aviation emissions are estimated to have continued to decline (by 1.0%) with emissions from international aviation rising by 4.0%.
2.3.4 International Aviation and Shipping
After peaking in 2008 at 3.1 MtCO2e, emissions from IAS were almost 0.7 MtCO2e lower in 2013 at 2.4 MtCO2e. The 2013 figure is marginally higher than the 2012 figure (<0.05 MtCO2e) but 6.4% below the 1990 figure. Between 2007 and 2010 the number of international flights from Scotland fell by 13.9% and emissions form international aviation fell by 21.1%. In the three years since 2010, international flight departures have risen by 17% and international aviation emissions are up by almost 12% or 0.11 MtCO2e.
The estimates for IS emissions fell by 3% in 2013 to just below 1.3 MtCO2e. This 2013 figure is the lowest figure since 2002 and 0.7 MtCO2e below the 1990 base year estimate.
The split in emissions between the two modes has changed over time with the share of the total coming from aviation rising from 20% in 1990 to almost 48% in 2013.
Rail emissions in 2013 remain under 0.2 MtCO2e, virtually unchanged from 2012. Although rail emissions are 55% above their equivalent 1990 figure rail emissions only account for 1.4% of all transport emissions in Scotland. Total passenger kilometres travelled by rail have increased by almost 40% for the period 2003-04 to 2013-14 and scheduled train kilometres have increased by almost 20% over the same period.
2.4 Road emissions by vehicle type
Emissions from cars have fallen from a peak of 6.1 MtCO2e in 2002 to an estimated 5.1 MtCO2e in 2013, a fall of 17%. Over the same period (2002-2013) car kilometres have risen from 33.1 billion kms to 33.8 billion kms. Compared to the 1990 base year car emissions have fallen by around 0.7 MtCO2e or 12%. Despite this fall, car emissions continue to account for the greatest proportion of road transport emissions at 54%. They also account for 39% of all transport emissions.
2.4.2 Heavy Goods Vehicles
HGV emissions make up the second largest proportion of road emissions and are estimated at 2.3 MtCO2e in 2013, the same as the 2012 estimate. HGV emissions fell slowly between 1990 and 2001 before growing rapidly. By 2006 HGV emissions surpassed their 1990 baseline figure of 2.1 MtCO2e reaching 2.2 MtCO2e in 2007. Emissions then fell in 2008 and 2009. Rises in the 2012 and 2013 have set new emissions peak for HGVs in each year.
2.4.3 Light Goods Vehicles
There has been a 78% increase in LGV emissions since 1990. At 1.4 MtCO2e in 2013 LGV emissions account for 15% of road emissions and 11% of total transport emissions. Emissions increased by almost 3% between 2012 and 2013 in line with the recent steady year on year increase in vehicle kilometres within this vehicle group.
Emissions from buses rose marginally between 2012 and 2013 and now account for just over 0.5 MtCO2e. Current bus emissions are though still 0.1 MtCO2e or 32% above the 1990 base year emissions estimate of just under 0.4 MtCO2e. Both vehicle kilometres and passenger journeys were stable between 2012/13 and 2013/14 but both are below their equivalent figure a decade ago.
Motorcycle emissions fell by 1% in 2013 compared to 2012 but remain at 0.03 MtCO2e and account for just 0.4% of road emissions and 0.3% of total transport emissions. There has been little change in either kilometres travelled or emissions since the base year.
Figures 11, 12 and 13 illustrate the changes in road emissions by vehicle type, the share of each vehicle type in total road emissions and the year in year change in car, HGV and LGV emissions respectively.
Figure 11 shows that goods vehicles were largely responsible for the increase in road emissions to 2007. Since then the decline in emissions from car has been behind the overall reduction in road emissions. The change in shares between vehicle types between 1990 and 2013 can be seen in Figure 12.
Figure 13 shows seven consecutive year-on-year falls in car emissions from 2007. The pattern with goods vehicles is more mixed with 2008 and 2009 being the only years in which there was a reduction in emissions for both goods vehicle types. Emissions from both rose in both 2012 and 2013.
2.5 Road emissions by road type
Emissions on rural roads have fallen for six consecutive years since 2007 although only very marginally in 2013. In 2013 rural road emissions are estimated at 4.6 MtCO2e. The latest year's estimate is almost 0.2 MtCO2e the base year figure of 4.8 MtCO2e. Rural emissions account for half of total road emissions.
At an estimated 2.7 MtCO2e in 2013, urban emissions are 10% below their 1990 level and down from a peak of 3.2 MtCO2e in 2007. Emissions from urban traffic currently account for just under 30% of road emissions.
At just over 20%, emissions from motorway traffic account for the smallest proportion of road emissions. At 1.9 MtCO2e they are though at their highest annual figure. The share in emissions from motorway traffic has been growing and shows a 51% increase over the share in 1990 (Figure 14).
The Light Goods Vehicle sector in Scotland
Light Goods Vehicles (LGVs) cover vans up to a laden weight of 3.5 tonnes and includes small car-like vans made by most vehicle manufacturers, transit vans, long wheelbase vans used by many of the parcel delivery companies, and Luton vans, often used for small house moves or clearances.
Number of vans in Scotland
At the end of 2003 there were 132,000 light goods vehicles registered in Scotland. By 2013 this figure had risen to 247,000, an increase of 115,000 or almost 90%. Over the same period the number of HGVs (>3.5 tonnes) fell from 45,000 to 36,000, a fall of just over one-fifth. As a share of all vehicles, vans have risen from 7.0% to 9.0%.
Numbers of kilometres travelled by vans in Scotland
LGV kilometres driven in Scotland are estimated to have risen steadily since 1995. Back in 1995 they stood at 3.8 billion kilometres. By 2003 they had topped 5 billion and it only took a further 4 years for the total distance to exceed 6 billion kilometres. The global recession then briefly reduced the total distance travelled but LGV kilometres are now on the rise again and reached a new peak distance of 6.3 billion kilometres in 2013. Since 1995 total kilometres have increased 2.4 billion or just under 65% (Figure B2). Over the same period, 1995-2013, total traffic kilometres rose by 7.1 billion kilometres so LGVs are responsible for 35% of the increase in total kilometres (Figure B3). In 1995 vans accounted for just over 10% of total vehicle kilometres. In 2013 this percentage has risen to 14.4%.
Just over 4 billion or 64% of current van kilometres are travelled on major (Motorway & Trunk) roads. A slightly smaller total and percentage of their total kilometres (3.6 billion and 57%) takes place on rural roads (rural roads includes motorway, trunk and minor roads) with 1.7 billion kilometres or 27% accounted for by driving on, mainly minor, urban roads.
Licenced LGVs: by engine cylinder size
Information is available on the engine size of the LGV, and while this does not also include load capacity there will be a strong correlation between load carrying capacity and engine size. Of course the load factor on an individual journey may be well below the load capacity of the vehicle.
The data on engine size shows that the proportion of vans with a cylinder size of 1500cc or below has fallen from 49% of the fleet in 1992 to 37% in 2015. Some of this may be due to the increasing efficiency of the engines, but the growth in the proportion of engines above 2000cc from around 8% of the fleet in 1992 to 17% in 2013 suggests that the payload capacity of the LGV fleet is increasing (Figure B4).
The most recent sales data from the Society of Motor Manufacturers and Traders (up to September 2015) covering the UK as a whole shows that there has been a strong growth in LGV sales across the board and but that there has been a particularly strong growth in the 2.5t - 3.5t van category.
|Year to date||% Share|
|Vans > 2.0 - 2.5t||44,602||15.7%|
|Vans > 2.5 - 3.5t||164,988||58.1%|
Source SMMT: vans sales and own calculation
Emissions from LGVs
With the rise in kilometres driven there has been a consequential rise in emissions from this vehicle category, particularly over the period 1990 to 1998. The introduction of the vehicle emissions directive restricting the emissions per kilometre along with the global recession has slowed the subsequent rate of emissions increase, particularly over the period since 2007 (Figure B5).
In 1995 emissions per kilometre were estimated to be around 230g CO2e/km. By 2000 this figure had hardly changed and even in 2013 the figure has only fallen to 225g CO2e/km. The 65% increase in kilometres marginally exceeds the 59% increase in LGV emissions. Obviously these high level averages cannot take account of payload weight in each period or the engine size changes over the years.
Future LGV use
The Department for Transport projections see kilometres travelled by heavy goods vehicles and cars increase by 44% and 37% respectively between 2010 and 2035; for light goods vehicles, which can weigh up to 3.5 tonnes fully laden, the expected rise is 87% - an annual average growth rate in kilometres travelled of 2.5%.
Table 1 sets out a number of comparisons between UK and Scottish emissions by broad sector or category, over both the short and longer term.
|Scottish emissions 2013 (ktCO2e)||UK emissions 2013 (ktCO2e)||Scottish emissions as a % of UK emissions 2013||Change in Scottish emissions (2012-13)||Change in UK emissions (2012-13)||Change in Scottish emissions (1990-2013)||Change in UK emissions (1990-2013)|
|All Transport (excl. IAS)||10,529||116,277||9.1%||-0.8%||-1.0%||-1.0%||-4.1%|
|Bus and coach||505||4,024||12.5%||3.5%||2.5%||31.9%||19.5%|
|Aviation Transport (incl. IA)||1,862||36,021||5.2%||2.0%||-1.0%||33.4%||69.9%|
|Maritime Transport (incl. IS)||1,592||11,317||14.1%||-4.3%||-3.4%||-38.7%||-8.8%|
- In 2013 Scottish transport emissions, including IAS, accounted for an estimated 8.2% of total UK transport emissions and 9.1% of emissions if IAS is excluded.
- The share of emissions from buses, traffic on rural roads, domestic and international maritime combined and from domestic aviation are disproportionately greater in Scotland than in the UK as a whole, with the opposite holding true for motorway emissions and international aviation. The shares in other categories are broadly similar to the overall picture.
- Between the 1990 base year and 2013, transport emissions in Scotland have fallen by 2.1% whereas for the UK as a whole they have risen by 7.8%. Without the inclusion of IAS the improvement for the UK as a whole (-4.1%) is greater than for Scotland alone (-1.0%)
- Over time, all sub-categories of Scottish transport emissions have tended to change broadly in line with the equivalent UK series.
- A number of sub categories (vans, motorway emissions, rail, bus and coach and international aviation) have seen sharp rises in emissions over the period 1990-2013 but in absolute terms it is only for vans and international aviation where the increase has been particularly significant.
- Scottish aviation emissions (with IA included) account for only 5.2% of the total UK aviation emissions but this percentage rises to 19.8% if only domestic aviation emissions are considered. This is to be expected given the relative importance of international aviation traffic (and emissions) in England relative to Scotland.
- Emissions from maritime transport in Scotland fell by 4.3% between 2012 and 2013, similar to but slightly greater than the UK reduction over the same period (3.4%). With IS included, maritime emissions in Scotland and in the UK are well below their respective 1990 figures (by 38.7% and 8.8% respectively).
Breaking down the UK estimates to the four home countries sheds a little more light on Scotland's performance relative to England, Wales and Northern Ireland.
- Compared with the 1990 base year, the Scottish aggregate emissions total (incl. IAS) shows a decrease of 2.1%. This is less of a reduction than in Wales but better than the outcome in both England and in N. Ireland where emissions have actually increased.
- Between 2012 and 2013 all four countries saw a reduction in their respective total emissions (incl. IAS).
|Road||Rail||Aviation||Aviation (incl.IA)||Maritime||Maritime (incl. IS)||All Transport||All Transport (incl. IAS)|
|Change in emissions||2012-13||-0.5%||-2.6%||-0.8%||2.0%||-10.0%||-4.3%||-0.8%||-0.6%|
|Change in emissions||2012-13||-0.8%||-3.0%||-4.5%||-1.1%||-5.2%||-3.4%||-1.0%||-1.1%|
|Change in emissions||2012-13||-0.5%||-2.1%||-9.6%||-5.8%||-2.0%||-2.6%||-0.7%||-1.0%|
|Change in emissions||2012-13||-1.1%||-1.3%||-2.5%||-6.3%||-2.6%||-2.7%||-1.2%||-1.7%|
2.7 Efficiency of passenger vehicles
Measuring the efficiency of passenger vehicles in terms of the CO2e per passenger kilometre (ppkm) provides another useful dimension for transport emissions - it helps consider relative efficiencies at mode level within the aggregate emissions story.
According to UK Company Reporting Guidelines, at just under 30g CO2e/ppkm a coach generates the least emissions per passenger kilometre, followed by rail at just under 45g CO2e/ppkm. The average diesel and petrol car produces emissions of 121g CO2e/ppkm and 127g CO2e/ppkm respectively, figures only exceeded by domestic flights with emissions of 158g CO2e/ppkm.
Table 5 also shows that, over time, almost all modes are seeing improvements in emissions per passenger kilometre, with rail and aviation seeing double digit improvements in performance. Since 1999 average car occupancy has fallen by 9.5% acting as a drag on the improved efficiency of the internal engine in terms of emissions per passenger kilometre.
Table 3: CO2e emissions per passenger kilometre by mode
|Sector||Mode and fuel||2012||2013||2014||2015||% Change 2012-2015|
|Road||Average petrol car||134||131||128||127||-5.3%|
|Average diesel car||124||121||123||121||-2.5%|
|Average petrol hybrid car||89||87||89||85||-3.9%|
|Average petrol motorbike||119||119||120||120||0.6%|
|Light rail and tram||68||60||62||55||-19.1%|
|Ferry (Large RoPax)||Average foot and car passengers||116||116||116||116||0.0%|
|Aviation||Average domestic flights||180||173||155||158||-12.5%|
|Average short haul international||104||102||88||90||-13.5%|
|Average long haul international||119||120||111||105||-11.8%|
Source: Government Conversion factors for company reporting http://www.ukconversionfactorscarbonsmart.co.uk/
2.8 Leading indicators
Data on Scottish greenhouse gas emissions emerges around 18 months after the end of the year in question. Unfortunately, there are not a large number of Scottish lead indicators that throw much light on performance in the period beyond the latest emissions data, but those that are available, including UK series, are discussed below and reported in Table 4.
- Road vehicle kilometres travelled: Road emissions are directly related to the kilometres travelled. This indicator tracks vehicle kilometres travelled by all vehicle types on all roads. From 2007 to 2011 the trend in total kilometres travelled in Scotland has been a slow decline. Since then total road kilometres have increased marginally year on year and in 2014 are back to 2007 levels.
- Proportion of new road vehicles that are alternatively fuelled: Alternatively fuelled vehicles, including electric and hybrid vehicles, produce fewer GHG emissions per kilometre travelled. An increase in the proportion of those vehicles on the road will reduce emissions from the transport sector. This indicator tracks the number of newly registered cars that received the Plug in Grant. 2014 saw a sharp increase in sales over 2013 and this trend has continued into 2015. This vehicle group does though still represent a very small proportion of total vehicles in Scotland and proportion of total vehicle kilometres travelled.
- Aviation movements: Emissions from international aviation in particular have grown rapidly over the past 20 years. This indicator tracks the total number of aviation movements at Scottish airports (take-off and landing) and shows another small increase between 2013 and 2014.
- 2014 UK provisional emissions estimates: Provisional UK emissions data for 2014 was published in March 2015 while final Scottish data for 2014 will not be published until June 2016. The latest UK transport emissions estimate shows a small increase in transport emissions taking them back to 2012 levels. This is the first reversal on a downward trend in emissions that begun after 2007. As yet there is no estimate available for 2014 emissions from International Aviation and Shipping. Even though there tends to be a strong correlation between emissions movements at the UK and Scottish levels there is no guarantee that this UK picture will be replicated in Scotland, particularly when international emissions estimates are unavailable and form a significant part of total Scottish transport emissions.
- Total transport fuel consumption: Improved fuel efficiency will reduce emissions per kilometre travelled. This indicator tracks total transport fuel sales and shows that total sales in 2014 decreased again, despite a small increase in both road and air activity.
- Average CO2/km of cars registered for first time: As the fleet becomes more fuel efficient and an increasing proportion of the fleet uses fuels other than mineral fuels so the average emissions of a newly registered car will fall. Table 4 shows there has been a fall in emissions per kilometre for both petrol and diesel engines between 2013 and 2014.
- Scottish GVA: Q1 2013 to Q1 2014: over the year to the end of the second quarter of 2014 Scottish GVA grew by 3.1%. While economic performance and emissions remain so strongly linked, an improving economic performance is likely to put upward pressure on Scottish emissions. This pressure will be felt not just in the transport sector where goods vehicle kilometres and private mileage have tended to increase during periods of economic growth but across other sectors of the economy too.
- Scottish forecourt pump prices Q1 2013 to Q1 2014: after a number of years of significant fuel price rises the trend was reversed in the last quarter of 2013 and pump prices have fallen sharply since and this has continued into 2015. 2015 prices are back to levels not seen since the beginning of 2010. While demand for fuel is generally inelastic (price changes have little impact on demand for fuel) the reduction in fuel prices is likely to see a small increase in demand for fuel at the forecourts.
Together, the available indicators suggest that pressure is building on Scottish transport emissions with a number of key indicators moving in a direction that, if continued will lead to an increase in emissions in the near future. As cars become a smaller share of total transport emissions so the aggregate impact of the measures to reduce car emissions declines.
Average growth p.a.
Scottish vehicle kilometres travelled
Sales of Plug in Grant eligible cars
Aircraft movements at Scottish
UK transport emissions (excl. IAS)
UK domestic petroleum consumption
by transport (million tonnes)
Average CO2/km of petrol cars
registered for first time
Average CO2/km of diesel cars
registered for first time
|Q1 2013 - Q1 2014|
Scottish year-on-year GVA growth
(to Q1 2014)
Scottish year-on-year change in
a) petrol and b) diesel prices