Economic, Environmental and Social Impacts of Changes in Maintenance Spend on Local Roads in Scotland

Appendix I Analysis of Emissions and Air Quality

I.1 Methodology

The emissions analysis includes 3 separate components as follows:

• The carbon costs of emissions from vehicles travelling over the road network under normal running conditions, where changes in the carriageway roughness have an impact on vehicle emissions: modelled using the HDM-4 emissions model.
• The carbon costs of emissions from vehicles delayed through roadwork sites either due to a reduction in speed or due to idling at traffic lights: modelled using the emissions model in the DfT Queues and Delays at Roadworks (QUADRO) model.
• The costs of embodied CO₂e (carbon dioxide equivalents) in carriageway maintenance materials and the activities carried out during carriageway maintenance (e.g. fuel consumed by plant): modelled using the treatment extent information and default values of CO₂e from the asPECT tool (Wayman, Schiavi-mellor, & Cordell, 2011).

I.1.1 Methodology for the calculation of carbon emissions vehicles under normal running conditions

The methodology adopted was identical to the methodology described in Appendix F for the calculation of VOCs with the following differences:

• Instead of the VOC outputs from HDM-4 the emissions outputs were used, specifically the kg of C0₂ figures reported for each of the model runs.
• The projected increase in fuel efficiency for each vehicle type was used with the mass of CO₂ from the HDM-4 runs to determine the time variation in emissions for each vehicle type.
• The increase in the cost of carbon was included in the analysis using the central non-traded carbon costs from webTAG. Note that the mass of CO₂ was converted to a mass of Carbon using the ratio of the atomic mass of carbon and C0₂ (12/44).

I.1.2 Methodology for the calculation of carbon costs from vehicles delayed through roadworks.

The methodology adopted was identical to the methodology used to calculate the user delay costs due to roadworks described in Appendix H but the CO₂ cost outputs from the QUADRO model were used in place of the delay cost outputs.

I.1.3 Methodology for the calculation of carbon costs from embodied carbon in road maintenance materials and works activities

Using the treatment lengths and areas from the WDM model runs the area of treatment for each road type over each interval was divided using the same methodology as described in Section H.1. This provided a treatment area for each treatment type in each of the analysis years for each Scenario and sample Authority. To determine the volume of materials, asphalt thicknesses were assumed for the 3 different treatment types as shown in Table I.1

Table I.1 Treatment thicknesses for each treatment type

Treatment	Assumed Depth (mm)
Reconstruction	200
Strengthening	40
Resurfacing	15

Using default carbon footprint data from the asPECT carbon footprinting tool and the density of asphalt the corresponding mass and embodied carbon dioxide equivalents were calculated for each sample Authority and analysis year under the 3 scenarios. The data used for this calculation is shown in Table I.2.

Table I.2 Density and embodied CO2 data for maintenance treatments

Treatment	Embodied CO2e by volume of asphalt (kgCO2e/m3)
Reconstruction	104
Strengthening	104
Resurfacing	104

Finally the equivalent mass of carbon was calculated using the ratio of the atomic mass between carbon and CO₂ (12/44) and the resulting mass of carbon was costed using the central non-traded price of carbon from webTAG (Department for Transport, 2011a).

I.1.4 Methodology for calculating other pollutants.

Using the calculated carbon costs a mass of CO₂ was back calculated using the central non-traded cost of carbon from webTAG and the ratio of the atomic mass of carbon dioxide to carbon (44/12). From this it was possible to calculate the mass of the other combustion products using proportions derived from the Emission Factors Toolkit for Vehicle Emissions, version 4.2.2 (DEFRA, 2009).

I.2 Results

I.2.1 Carbon costs from vehicles using the network under normal running conditions

Figure I.1 to Figure I.8 show the carbon emissions from vehicles using the network under normal running conditions for the 8 sample Authorities. Whilst the magnitude of these numbers is much larger than the emissions due to roadworks the difference between Scenarios 2 and 3 and the base scenario (Scenario 1) is relatively small at approximately £4m at the point of greatest difference (Scenario 3 compared with Scenario 1 in 2030). The general upwards trend of the graphs is due to increasing traffic with time.

Figure I.1 Aberdeenshire carbon costs for vehicle normal running
(2002 prices undiscounted)

Figure I.2 Dumfries and Galloway carbon costs for vehicle normal running
(2002 prices undiscounted)

Figure I.3 City of Edinburgh carbon costs for vehicle normal running
(2002 prices undiscounted)

Figure I.4 Fife carbon costs for vehicle normal running
(2002 prices undiscounted)

Figure I.5 Glasgow City carbon costs for vehicle normal running
(2002 prices undiscounted)

Figure I.6 Highland carbon costs for vehicle normal running
(2002 prices undiscounted)

Figure I.7 North Lanarkshire carbon costs for vehicle normal running
(2002 prices undiscounted)

Figure I.8 South Ayrshire carbon costs for vehicle normal running
(2002 prices undiscounted)

I.2.2 Carbon costs from delayed vehicles through roadworks

The increase in carbon emissions, and costs, from vehicles delayed through roadwork sites is shown for the 8 sample Authorities in Figure I.9 to Figure I.16. These results show that with decreasing maintenance spend there is correspondingly less maintenance works on the network and consequently a reduction in vehicle delays. This analysis does not include consideration of delays caused by unplanned maintenance, which may increase as planned maintenance activities are reduced.

Figure I.9 Aberdeenshire carbon costs from vehicles delayed at roadworks
(2002 prices undiscounted)

Figure I.10 Dumfries and Galloway carbon costs from vehicles delayed at roadworks
(2002 prices undiscounted)

Figure I.11 City of Edinburgh carbon costs from vehicles delayed at roadworks
(2002 prices undiscounted - Note changed scale for costs in Figure I.11)

Figure I.12 Fife carbon costs from vehicles delayed at roadworks
(2002 prices undiscounted)

Figure I.13 Glasgow City carbon costs from vehicles delayed at roadworks
(2002 prices undiscounted)

Figure I.14 Highland carbon costs from vehicles delayed at roadworks
(2002 prices undiscounted)

Figure I.15 North Lanarkshire carbon costs from vehicles delayed at roadworks
(2002 prices undiscounted)

Figure I.16 South Ayrshire carbon costs from vehicles delayed at roadworks
(2002 prices undiscounted)

I.2.3 Carbon costs from maintenance works (embodied CO₂)

Maintenance works include embodied CO2 from the use of plant and materials. Therefore, as maintenance budgets are reduced and less maintenance is carried out the amount of embodied CO2 reduces. The results of the embodied CO2 analysis are shown in Figure I.17 to Figure I.24.

Figure I.17 Aberdeenshire carbon costs from embodied CO₂
(2002 prices undiscounted)

Figure I.18 Dumfries and Galloway carbon costs from embodied CO₂
(2002 prices undiscounted)

Figure I.19 City of Edinburgh carbon costs from embodied CO₂
(2002 prices undiscounted)

Figure I.20 Fife carbon costs from embodied CO₂
(2002 prices undiscounted)

Figure I.21 Glasgow City carbon costs from embodied CO₂
(2002 prices undiscounted)

Figure I.22 Highland carbon costs from embodied CO₂
(2002 prices undiscounted)

Figure I.23 North Lanarkshire carbon costs from embodied CO₂
(2002 prices undiscounted)

Figure I.24 South Ayrshire carbon costs from embodied CO₂
(2002 prices undiscounted)

I.3 Effect of discounting

The results of taking the data from Fife and discounting the costs at 3.5% per year to 2010 (in 2002 prices) are shown in Figure I.25 to Figure I.27.

Figure I.25 Fife carbon costs for vehicle normal running
(2002 prices discounted)

Figure I.26 Fife carbon costs from vehicles delayed at roadworks
(2002 prices discounted)

Figure I.27 Fife carbon costs from embodied CO₂
(2002 prices discounted)

I.4 Air quality

Results from the air quality assessment are summarised in Table I.3 and Table I.4.

Table I.3 Nitric Oxide and Nitrogen Dioxide (NOx) and Hydrocarbon emissions

Year	NOx (tonnes)			Hydrocarbon (tonnes)
	Scenario 1	Scenario 2	Scenario 3	Scenario 1	Scenario 2	Scenario 3
2011	0.0472	0.0471	0.0469	0.0090	0.0090	0.0089
2012	0.0474	0.0473	0.0472	0.0090	0.0090	0.0090
2013	0.0476	0.0475	0.0474	0.0091	0.0090	0.0090
2014	0.0477	0.0476	0.0475	0.0091	0.0091	0.0090
2015	0.0478	0.0477	0.0476	0.0091	0.0091	0.0091
2016	0.0478	0.0477	0.0477	0.0091	0.0091	0.0091
2017	0.0479	0.0478	0.0477	0.0091	0.0091	0.0091
2018	0.0479	0.0478	0.0478	0.0091	0.0091	0.0091
2019	0.0478	0.0477	0.0477	0.0091	0.0091	0.0091
2020	0.0476	0.0476	0.0476	0.0091	0.0091	0.0091
2021	0.0475	0.0475	0.0475	0.0090	0.0090	0.0091
2022	0.0473	0.0473	0.0473	0.0090	0.0090	0.0090
2023	0.0471	0.0471	0.0471	0.0090	0.0090	0.0090
2024	0.0469	0.0469	0.0469	0.0089	0.0089	0.0089
2025	0.0467	0.0467	0.0467	0.0089	0.0089	0.0089
2026	0.0465	0.0465	0.0466	0.0089	0.0089	0.0089
2027	0.0466	0.0466	0.0467	0.0089	0.0089	0.0089
2028	0.0467	0.0467	0.0468	0.0089	0.0089	0.0089
2029	0.0468	0.0468	0.0469	0.0089	0.0089	0.0089
2030	0.0469	0.0469	0.0470	0.0089	0.0089	0.0089
Total	0.9455	0.9446	0.9446	0.1800	0.1799	0.1798

 

Table I.4 Particulate Matter (PM2.5 and PM10) emissions

Year	PM2.5 (tonnes)			PM10 (tonnes)
	Scenario 1	Scenario 2	Scenario 3	Scenario 1	Scenario 2	Scenario 3
2011	0.0028	0.0028	0.0028	0.0041	0.0040	0.0040
2012	0.0028	0.0028	0.0028	0.0041	0.0041	0.0041
2013	0.0028	0.0028	0.0028	0.0041	0.0041	0.0041
2014	0.0028	0.0028	0.0028	0.0041	0.0041	0.0041
2015	0.0028	0.0028	0.0028	0.0041	0.0041	0.0041
2016	0.0028	0.0028	0.0028	0.0041	0.0041	0.0041
2017	0.0028	0.0028	0.0028	0.0041	0.0041	0.0041
2018	0.0028	0.0028	0.0028	0.0041	0.0041	0.0041
2019	0.0028	0.0028	0.0028	0.0041	0.0041	0.0041
2020	0.0028	0.0028	0.0028	0.0041	0.0041	0.0041
2021	0.0028	0.0028	0.0028	0.0041	0.0041	0.0041
2022	0.0028	0.0028	0.0028	0.0041	0.0041	0.0041
2023	0.0028	0.0028	0.0028	0.0041	0.0041	0.0041
2024	0.0028	0.0028	0.0028	0.0040	0.0040	0.0040
2025	0.0027	0.0027	0.0027	0.0040	0.0040	0.0040
2026	0.0027	0.0027	0.0027	0.0040	0.0040	0.0040
2027	0.0027	0.0027	0.0027	0.0040	0.0040	0.0040
2028	0.0027	0.0027	0.0027	0.0040	0.0040	0.0040
2029	0.0027	0.0027	0.0028	0.0040	0.0040	0.0040
2030	0.0028	0.0028	0.0028	0.0040	0.0040	0.0040
Total	0.0555	0.0555	0.0555	0.0814	0.0813	0.0813

Notes: PM10 - Particulate Matter < 10 µm

PM2.5 - Particulate Matter < 2.5 µm