Carbon Account for Transport

Carbon Account for Transport No. 8: 2016 Edition

Carbon Account for Transport

Chapter 2: Historical emissions analysis

2.1 Background and data sources

All of the emissions data presented in this chapter is from the Greenhouse Gas Inventory for England, Scotland, Wales and Northern Ireland: 1990-2014[7] (GHGI), unless otherwise stated. Further to the information presented in this report, data referring to emissions from other sectors in Scotland is published in the Official Statistics release Scottish Greenhouse Gas Emissions 2014[8] The GHGI is compiled on an annual basis and a complete time series of all greenhouse gases dating back to 1990 is updated in each publication. This is to account for improvements in data and advances in calculation methodology. Revisions to the GHGI have led to a significant increase in the base year Scottish emissions figure for 1990 which has consequently impacted the absolute emissions reduction required to meet climate change targets. The greenhouse gases associated with transport recorded by GHGI are carbon dioxide (CO2), nitrous oxide (N2O) and methane (CH4)[9]. Emissions levels are presented in mega-tonnes of carbon dioxide equivalent (MtCO2e), a common unit which converts the mass of other gases to a mass of CO2 which has the equivalent environmental impact.

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, indicative assessments of emissions from IAS have been included in the datasets since 2009. Furthermore, in line with the Scottish Government's commitment to include IAS emissions in the targets set by the Climate Change (Scotland) Act 2009, references to aviation and maritime emissions refer to both domestic and international combined, 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 or displaced impacts, such as the emissions generated by the electricity used on electrified railways, are included.

As well as including 2014 emissions data for the first time, the 2014 publication also updates emission estimates for all previous years, incorporating methodological changes and updates. As the emissions inventory contains no data for the periods 1991 to 1994, and from 1996 to 1997 inclusive gaps have been added to some graphs to more accurately show the rate of change over the entire time period.

2.2. Total emissions trends for Scotland and the Scottish transport sector

In 2014 total Scottish emissions from all sectors amounted to 46.7 MtCO2e[10]. This total represents a 4.4 MtCO2e or 8.6% reduction from the 2013 figure. Compared to the 1990 base year Scotland has reduced its total emissions by 39.6%.

Transport's share of total emissions is 12.9 MtCO2e. After almost continual increases in transport emissions from 1990, they peaked in 2007 at 14.9 MtCO2e. Transport emissions have since fallen year on year and are now below their 1990 base year level of 13.2 MtCO2e and 13.3% below the 2007 peak.

The run in emissions reductions has been as a result of a number of factors. Principal among them was the consequences from the recession that began in 2008, and the slow recovery which followed. Further to this, investment in public transport infrastructure, improvements in fuel efficiency, government emissions policies, land-use planning and high global oil prices helped to cut transport emissions. However, global oil prices peaked in 2014 and began to fall significantly afterwards, which may have resulted in an increase in demand for fuel and travel.

With IAS emissions excluded, the transport sector accounts for 24% of all Scottish emissions. Including IAS, this proportion rises to just below 28%. Figure 1 illustrates the growing relative importance of transport emissions in Scotland's emissions total.

Figure 1: Total emissions from transport and transport emissions as a percentage of total Scottish emissions, 1990-2014
Figure 1: Total emissions from transport and transport emissions as a percentage of total Scottish emissions, 1990-2014
Source: Greenhouse Gas Inventory, NAEI, 2016, 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. This category accounts for 9.4 MtCO2e, or 73% of transport emissions in 2014. This is marginally higher than the 2013 figure.

Figure 2 shows that road emissions followed a generally rising trend from 1990 to peak at 10.3 MtCO2e 2007. Since then, road emissions have fallen for five out of the seven years to 2014. Total road kilometres in 2014 were 2.8% higher than they were in 2007, implying an increase in fuel efficiency for road vehicles. Nonetheless, road emissions were almost 3% higher in 2014 than in 1990.

Figure 2: Road transport emissions and road transport emissions as a share of total transport emissions, 1990-2014
Figure 2: Road transport emissions and road transport emissions as a share of total transport emissions, 1990-2014

Figure 3 shows the growth in goods vehicle emissions relative to those of cars. While the share of road emissions from cars has fallen marginally between 1990 and 2014, total goods vehicle emissions have risen from just under 30% to just over 34% in the same period, with an increasing prominence for emissions from LGVs.

As well as reflecting improvements in fuel efficiency, car emissions have also been affected by a shift in fuel preferences. Diesel engines are more fuel efficient than their petrol equivalents, and so the increased proportion of the fleet fuelled by diesel since 1999 (as shown in figure 4) has resulted in a reduction in GHG emissions.

Figure 3: Distribution of road transport emissions by mode – selected years
Figure 3: Distribution of road transport emissions by mode – selected years

Figure 4: Distribution of new Scottish registrations between petrol and diesel, 1999-2014 – all vehiFigure 4: Distribution of new Scottish registrations between petrol and diesel, 1999-2014 – all vehicle body typescle body types

Should the split in new registrations between diesel and petrol settle around a 50:50 split, this year on year reduction in total emissions from switching to diesel will not continue. Further analysis of road transport emissions is undertaken in sections 2.4 and 2.5.

2.3.2 Maritime Transport

Emissions from maritime transport[11] in 2014 are estimated to be 1.4 MtCO2e or 11% of total transport emissions. Figure 5 shows that emissions from this sector have been volatile, due at least in part to methodological and GHG reporting changes.

Figure 5: Maritime transport emissions and maritime transport emissions as a share of total transport emissions, 1990-2014
Figure 5: Maritime transport emissions and maritime transport emissions as a share of total transport emissions, 1990-2014

More recently, maritime emissions peaked at 2.4 MtCO2e in 2008 before falling to a new low in 2014, 46% below the 1990 figure. The volatility in the series can be attributed to the performance of international shipping sector (IS), which historically account for more than 70% of all maritime emissions, as indicated in figure 6. This figure also shows domestic maritime emissions decreasing over time.

Figure 6: Comparison between domestic and international shipping emissions
Figure 6: Comparison between domestic and international shipping emissions

2.3.3 Aviation

In 2014 aviation emissions stood at 1.9 MtCO2e. This represents an increase of less than 0.1 MtCO2e over 2013, but they now stand 38% above the equivalent 1990 figure, and account for 15% of all transport emissions. Figure 7 shows an increasing trend in emissions from 1990 to 2007, peaking at 2.3 MtCO2e before the recent recession led to lower annual emissions until 2010. There has subsequently been a slow increase in aviation emissions.

Figure 8 shows that from 1998 to 2004 emissions from domestic and international aviation were very similar. The series have since diverged. In 2014 international aviation emissions are estimated to account for 63% of total Scottish aviation emissions, almost the reverse of the proportion in 1990 when it was domestic aviation emissions that accounted for 61% of aviation's total. Between 2013 and 2014 domestic aviation emissions are estimated to have continued to decline (by 4.0%) with emissions from international aviation rising by 5.5%.

Figure 7: Aviation transport emissions and aviation transport emissions as a share of total transport emissions, 1990-2014
Figure 7: Aviation transport emissions and aviation transport emissions as a share of total transport emissions, 1990-2014

Figure 8: Comparison between domestic and international aviation emissions
Figure 8: Comparison between domestic and international aviation emissions

2.3.4 International Aviation and Shipping

After peaking in 2008 at 3.1 MtCO2e, emissions from IAS were 0.8 MtCO2e lower in 2014 at 2.3 MtCO2e. The 2014 figure is marginally lower than the 2013 figure (by approximately 0.06 MtCO2e) and 11% below the 1990 figure. Between 2007 and 2010 the number of international flights from Scotland fell by 13.9% and emissions from international aviation fell by 21.2%. In the four years since 2010, international flight departures have risen by 18% and international aviation emissions are up by almost 19.5% or 0.2 MtCO2e.

The estimates for IS emissions fell by 10% in 2014 to just below 1.1 MtCO2e. This 2014 figure is the lowest figure since 2008 and 0.95 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 21% in 1990 to almost 53% in 2014.

Figure 9: International maritime and aviation emissions, 1990-2014
Figure 9: International maritime and aviation emissions, 1990-2014

2.3.5 Rail

Rail emissions in 2014 remain under 0.2 MtCO2e, which is 1.35% of all transport emissions in Scotland. However, this is 40.0% above the 1990 figure. Total passenger kilometres travelled by rail have increased by 50% for the period 2003-04 to 2014-15[12] and scheduled train kilometres have increased by 22% over the same period.

Figure 10: Rail transport emissions and rail transport emissions as a share of total transport emissions, 1990 - 2014
Figure 10: Rail transport emissions and rail transport emissions as a share of total transport emissions, 1990 - 2014

2.4 Road emissions by vehicle type[13]

2.4.1 Cars

Emissions from cars have fallen from a peak of 6.3 MtCO2e in 2007 to an estimated 5.7 MtCO2e in 2014. Over the period 2002-2014, car kilometres have risen from 33.1 billion kms to 34.4 billion kms while emissions over the same period have fallen by from 6.3 MtCO2e to 5.7 MtCO2e. Despite this fall, car emissions continue to account for the greatest proportion of road transport emissions at 60% and almost 44% of all transport emissions in Scotland.

2.4.2 Heavy Goods Vehicles

HGV emissions make up the second largest proportion of road emissions at 1.68 MtCO2e in 2014. HGV emissions fell slowly between 1990 and 2001 before growing again, peaking at 1.88 Mt CO2e in 2007. HGV emissions have fluctuated around 1.7 MtCO2e since 2009.

2.4.3 Light Goods Vehicles

There has been a 61% increase in LGV emissions since 1990. At 1.54 MtCO2e in 2014, LGV emissions account for 16% of road emissions and 12% of total transport emissions. Emissions increased by over 4% between 2013 and 2014 in line with the steady year on year increase in vehicle kilometres of this group.

2.4.4 Buses

Emissions from buses have been flat since 2011 at just under 0.5 MtCO2e; 0.1 MtCO2e (19%) below the 1990 figure. Vehicle kilometres were stable between 2013 and 2014 but there was a 2.4% drop in passenger journeys.

2.4.5 Motorcycles

Motorcycle emissions only accounted for 0.034 MtCO2e - 0.36% of road emissions and 0.26% of total transport emissions. Emissions from motorcycles have always been so small so as not to significantly impact on total Scottish transport emissions.

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 increasing goods vehicles emissions largely drove the increase in road emissions to 2007. The decline in emissions since then can be mainly attributed to cars. The change in shares between vehicle types between 1990 and 2014 can be seen in Figure 12.

Figure 13 shows that whereas previously changes in emissions tended to move in the same direction within a particular year this relationship seems to be less apparent in more recent years. The growth in van kilometres compared to other modes appears to generate the strongest recent trend.

Figure 11: Breakdown of road emissions by vehicle type, selected years
Figure 11: Breakdown of road emissions by vehicle type, selected years

Figure 12: Share of road emissions by vehicle type in 1990 and 2014
Figure 12: Share of road emissions by vehicle type in 1990 and 2014

Figure 13: Year on year change in car, HGV and LGV emissions 1999-2014
Figure 13: Year on year change in car, HGV and LGV emissions 1999-2014

2.5 Road emissions by road type[14]

2.5.1 Rural

2014 halted the downward trend in rural that began after 2007. This 2014 emissions estimate of 4.6 MtCO2e is the same at the 1990 estimate. Rural emissions account for 49% of total road emissions.

2.5.2 Urban

At just under 3 MtCO2e in 2014, urban emissions are 12% below their 1990 level of 3.4 MtCO2e, an emissions figure that was last recorded in 2007. Emissions from urban traffic account for just under 32% of road emissions.

2.5.3 Motorway

At 1.8 MtCO2e or 19%, emissions from motorway traffic account for the smallest proportion of 2014 road emissions. However, they are currently at their highest annual figure since 1990. Emissions from motorway traffic have increased by 59% over the 1990 figure (Figure 14).

Figure 14: Emissions by road type (Index=1990 for each road type)
Figure 14: Emissions by road type (Index=1990 for each road type)

Figure 15: Share of road emissions by road type
Figure 15: Share of road emissions by road type

Analysis of Low Emission Car and Van Sector

Given that road vehicles and cars and vans in particular generate the greatest proportion of carbon emissions (73%), it is impossible to meet the ambitious targets in the Climate Change Act without a fundamental transformation in how such vehicles are powered.

There are now a range of vehicles on the market which use a variety of technologies to produce lower, or in some cases zero emissions. Of these, this section of the report will focus on two: Plug-in Hybrid Electric Vehicles (PHEVs) and Battery Electric Vehicles (BEVs).

Plug-in Hybrid Electric Vehicles have two engines; one of which is an electric engine powered by a battery, and another which is a conventional internal combustion engine (ICE). The vehicle can run on one alone, or both can operate together to drive it. PHEVs differ from other forms of hybrid in that the battery which powers the electric motor is charged from an external power source in addition to any electricity generated through the internal combustion engine.

The result in emissions terms is that PHEVs generate lower carbon emissions than their ICE driven counterparts, especially over short journeys which can solely use the electric (i.e. zero emissions) powertrain.

BEVs are solely powered by a rechargeable battery, which can be recharged from an external power source. Such vehicles generate no emissions whatsoever during their operation. A key issue with currently available BEVs is the range capacity of the battery (typically around 100 miles although range is dependent on factors such as driving style and temperature). While this is not an issue for the overwhelming majority of current trips, for longer trips drivers become more reliant on publically available charging points. Research has shown that “range anxiety” is a significant factor for those considering buying a BEV, even if they very rarely make journeys beyond the range of the current battery.

The graph below shows the number of hybrid electric, and electricity powered vehicles registered in Scotland since 2010.

Incentives to drive a PHEV or BEV

There are currently a number of incentives and advantages available to assist with the purchase and running of PHEV and BEV cars and vans. The Plug-in Vehicle Grant offers drivers up to 35% of the cost of a new BEV or PHEV, up to a limit of £2,500 or £4,500 dependent on the model. Grants are also available to assist in the purchase of a van covering up to 20% of the cost with an upper cash limit of £8,000.

First time registrations and total number of Ultra Low Emission Vehicles in Scotland 2010-2015
First time registrations and total number of Ultra Low Emission Vehicles in Scotland 2010-2015
Source Department for Transport: 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 of CO2 have been included at this stage.

Sales have been boosted in Scotland by the provision of interest-free loans for BEV and PHEVs scheme, which are enabling individuals and businesses to make the switch. Furthermore, plug-in vehicles are currently exempt from VED, although this will change in 2017, as well as being exempt from schemes such as the London Congestion Charge. Company car tax is also lower for low emission vehicles.

The cost of running a BEV can be lower than that of a conventional ICE car 2-3p per mile compared to 16p per mile and the servicing and maintenance costs can be lower too.

Re-charging Infrastructure

The Scottish Government’s Second Report on Proposals and Policies (RPP2) states the intention to have a charging infrastructure in place in Scottish cities by 2020. The ChargePlace Scotland network of publically available EV charging infrastructure has expanded to over 600 points, equating to over 1200 charging bays. This includes over 150 ‘rapid’ charge points, one of the most comprehensive networks in Europe.

The map shows the distribut ion of these “rapid” charge points across Scotland (as at July 2016).

ChargePlace Scotland, 50kW Rapid Charge Points, July 2016
ChargePlace Scotland, 50kW Rapid Charge Points, July 2016

Popular Plug In Vehicles

Across the UK the most popular plug-in vehicle in the UK is the Mitsubishi Outlander PHEV, with approximately 25,000 units on the road in 2016. The most popular BEV in the UK is the Nissan Leaf, which is also the world’s most popular all-electric vehicle, with approximately 240,000 units sold since its introduction to market in 2010.

More manufacturers and more models are expected to be released onto the UK market in the next couple of years increasing the options for consumers.

2.6 Comparison of key Scottish and UK transport emission statistics

Table 1 sets out a number of comparisons between UK and Scottish emissions by broad sector or category, and over both the short and longer term.

Table 1: Comparison of Scottish and UK GHG emissions
Scottish emissions 2014 (ktCO2e) Scottish emissions as a % of UK emissions 2014 Change in Scottish emissions (2013-14) Change in UK emissions (2013-14) Change in Scottish emissions (1990-2014) Change in UK emissions (1990-2014)
All Transport 12,924 8.2% 0.0% 0.4% -2.8% 8.4%
All Transport (excl. IAS) 10,646 9.0% 0.5% 1.1% -0.8% -3.3%
Road Transport 9,434 8.6% 0.9% 1.4% 2.7% -1.2%
of which:            
Cars 5,658 8.3% 0.7% 0.8% -2.3% -5.1%
HGVs 1,675 9.0% -1.0% 1.4% -6.3% -9.1%
LGVs 1,542 8.9% 4.1% 4.0% 61.2% 48.1%
Bus and coach 480 12.5% -0.1% -0.7% -19.5% -27.0%
Motorcycles 34 6.5% 4.5% 3.9% -2.3% -32.4%
Rural 4,629 10.8% 1.0% 2.1% -0.1% 2.4%
Urban 2,969 7.3% 1.0% 1.0% -12.7% -17.2%
Motorway 1,776 7.1% 0.5% 0.8% 58.7% 29.7%
Rail Transport 174 7.9% 1.7% 1.3% 40.0% 4.2%
Aviation Transport 622 20.7% -5.0% -8.6% -22.2% -44.2%
Aviation Transport (incl. IA) 1,918 5.3% 1.7% -0.1% 38.2% 72.1%
Maritime Transport 325 11.0% 0.8% 0.1% -44.0% -19.6%
Maritime Transport (incl. IS) 1,398 13.3% -7.9% -7.0% -46.2% -15.2%
  • In 2014 Scottish transport emissions, including IAS, accounted for an estimated 8.2% of total UK transport emissions and 9.0% 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 2014, transport emissions in Scotland have fallen by 2.8% whereas for the UK as a whole they have risen by 8.4%. Without the inclusion of IAS the improvement for the UK as a whole (-3.3%) is greater than for Scotland alone (-0.8%)
  • 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 1990-2014 but in absolute terms it is only for vans and international aviation where the increase has been particularly significant.
  • Total Scottish (Domestic and International) aviation emissions account for 5.3% of the total UK aviation emissions, but 20.7% of total UK domestic aviation emissions. This is to be expected given the relative importance of international aviation traffic (and emissions) in England in particular relative to Scotland.
  • Emissions from domestic maritime transport in Scotland fell by 7.9% between 2013 and 2014, a similar but slightly greater reduction than the UK figure over the same period (7.0%). With IS included, maritime emissions in Scotland and for the UK are notably below their respective 1990 figures.

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 2.8%. This is less of a reduction than in Wales but better than the outcome in both England and in N. Ireland where emissions have risen over the same period.
  • Between 2013 and 2014 all four countries saw small increases in emissions, excluding International Aviation and Shipping.
Table 2: Comparison of Scottish, English Welsh and Northern Irish GHG emissions from transport 1990 – 2014 and 2013 – 2014
    Road  Rail Aviation  Aviation (incl.IA)  Maritime Maritime (incl. IS) All Transport All Transport  (incl. IAS) 
SCOTLAND Emissions 2014 9,434 174 714 1,918  325  1,398  10,646  12,924
Change in emissions  2013-14 0.9% 1.7% -4.0% 1.7% 0.8% -7.9% 0.5% 0.0%
1990-2014 2.7% 40.0% -16.0% 38.2% -44.0% -46.2% -0.8% -2.8%
ENGLAND Emissions 2014 90,361 1,734 2,537 34,082  2,312  7,620  96,944  133,798
Change in emissions  2013-14 1.4% 1.3% -7.2% -0.1% 0.4% -5.5% 1.1% 0.6%
1990-2014 -2.7% -0.5% -42.2% 76.8% -15.1% -7.0% -4.7% 9.6%
WALES Emissions 2014 5,547 97 63 125  216  1,023  5,923  6,792
Change in emissions  2013-14 1.7% 1.3% -11.6% -11.3% -4.2% -15.0% 1.3% -1.5%
1990-2014 -0.6% 40.5% -63.9% -50.5% -20.0% -13.3% -2.8% -4.1%
N.IRELAND Emissions 2014 3,955 39 233 340  110  133  4,338  4,467
Change in emissions  2013-14 1.2% 2.2% -11.0% -7.7% 1.0% 0.6% 0.5% 0.5%
1990-2014 33.6% 55.1% 0.6% 6.1% 0.7% 12.0% 30.4% 30.4%

2.7 Efficiency of passenger vehicles

Measuring the efficiency of passenger vehicles in terms of the CO2e per passenger kilometre (ppkm)[15] provides another useful lens for considering transport emissions.

According to UK Company Reporting Guidelines[16], on average a UK coach generates the least emissions per passenger kilometre at 29g CO2e/ppkm, followed by rail at 49g CO2e/ppkm. The average diesel and petrol car produces emissions of 122g CO2e/ppkm and 128g CO2e/ppkm respectively; emissions levels per kilometre which are only exceeded by domestic flights at 147g 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 11.2%[17], which has acted as a drag on the improved efficiency of the internal combustion engine in terms of emissions per passenger kilometre.

Table 3: CO2e emissions per passenger kilometre by mode[18]
Sector Mode and fuel gCO2e/ppkm
2012 2013 2014 2015 2016 % Change 2012-2016
Road Average petrol car 134 131 128 127 128 -4.3%
Average diesel car 124 121 123 121 122 -1.4%
Average petrol hybrid car 89 87 89 85 88 -0.6%
Average petrol motorbike 119 119 120 120 120 0.7%
Average bus 112 112 109 109 102 -9.1%
Average coach 29 29 29 29 29 -0.2%
Rail National rail 58 49 47 45 49 -16.0%
Light rail and tram 68 60 62 55 54 -20.6%
Ferry (Large RoPax) Average foot and car passengers 116 116 116 116 116 0.0%
Aviation Average domestic flights 180 173 155 158 147 -18.1%
Average short haul international 104 102 88 90 89 -14.2%
Average long haul international 119 120 111 105 101 -14.7%

Source: Government Conversion factors for company reporting (advanced users workbook), available at

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 after the latest emissions data to the present date, but those that are available, including UK series, are reported and discussed below.

  • Scottish road vehicle kilometres travelled: This indicator tracks vehicle kilometres travelled by all vehicle types on all roads. Road emissions are directly related to the kilometres travelled. From 2007 to 2011 total kilometres travelled annually in Scotland declined slowly. Since then, they have increased marginally year on year and in 2015 surpassed the previous peak in 2007.
  • Sales of Plug in Grant eligible cars: This indicator includes electric and hybrid vehicle and produce less GHG emissions per kilometre travelled. An increase in the proportion of such vehicles on the road will reduce average transport emissions. It is calculated from the number of newly registered cars that received the Plug-in Grant. The latest data shows that 2015 saw a sharp increase in sales of 56% over 2015, and this trend has continued into 2016. However, alternatively fuelled vehicles still represent a very small proportion of total registered vehicles in Scotland (0.6%) 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), which shows a small decrease of approximately 0.6% between 2014 and 2015.
  • 2015 UK provisional emissions estimates: Provisional UK emissions data for 2015 has been published, while the Scottish emissions inventory for 2015 will not be available until June 2017. The provisional UK transport estimate shows a small increase in emissions of 1.4%. This is the second consecutive year of growth in this indicator, continuing the reversal on a downward trend in emissions that began after 2007. There is currently no estimate available for 2015 emissions from International Aviation and Shipping. Though there tends to be a strong correlation between emissions movements at the UK and Scottish levels, there is no guarantee of this, particularly when international emissions figures are unavailable and form a significant proportion of Scottish transport emissions.
  • UK domestic transport fuel consumption: This indicator tracks total transport fuel sales and shows that total sales in 2015 increased by 2.1% on the previous year. Improved fuel efficiency will reduce emissions per kilometre travelled, but if overall road kilometres are rising along with fuel consumption emissions from road transport are likely to increase.
  • Average CO2/km of cars registered for first time: As internal combustion engines becomes more fuel efficient and an increasing proportion of cars use alternative fuels, the average emissions of a newly registered car will fall. Table 4 shows falling emissions per kilometre for both petrol and diesel engines between 2014 and 2015.
  • Scottish GDP: Q2 2015 to Q2 2016: over the year to the end of the second quarter of 2016 Scottish GDP grew by 0.7%. This indicates that growth is slowing in comparison to previous years. Because economic performance and emissions remain strongly linked, slower GDP growth is likely to result in slower emissions growth.
  • Scottish forecourt pump prices October 2015 to October 2016: prices of both petrol and diesel increased in the above period by 4.9% and 4.7% respectively which is likely to have a marginally negative impact on sales figures.

Together, the available indicators suggest that achieving reductions in Scottish transport emissions is becoming more challenging, with a number of these key leading indicators suggesting a possible increase in emissions. As cars become a smaller share of total transport emissions so the aggregate impact of the measures to reduce emissions from car declines and other sectors such as goods vehicles and aviation become relatively more important to the overall position in transport.

Table 4: Trends in leading transport indicators
Indicator 2014 2015 Average growth p.a. Growth
      (2003-2015) (2014-2015)
Road vehicle kilometres travelled
(million vehicle kilometres)
44.5 45.0 0.6% 1.3%
Sales of Plug in Grant eligible cars (Scotland) 834 1298 - 55.6%
Aircraft movements 482,878 480,070 1.4% -0.6%
UK transport emissions (excl. IAS) (MtCO2e) 116.6 118.3 -0.6% 1.4%
UK domestic transport fuel consumption (million tonnes) 35.001 35.738 -0.9% 2.1%
Average CO2/km of petrol cars registered for the first time 128.4 126.7 2003 Data Unavailable -1.4%
Average CO2/km of diesel cars registered for the first time 122.8 120.7 2003 Data Unavailable -1.7%
Scottish year-on-year GVA growth (to Q2 2016) - - - 0.7%
Scottish year-on-year change in a) petrol and b) diesel prices (October 15 - October 16)       a) 4.9%
b) 4.7%