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

Appendix C Summary of Key Data and Assumptions

Key economic information including the cost of carbon, value of time and improvements in vehicle efficiency were taken from data published in STAG (Transport Scotland, 2011a) and the Department for Transport Analysis Guidance (webTAG) website (Department for Transport, 2011a).

Note that the analysis of Vehicle Operating Costs used the HDM-4 model produced by HDM-4 Global not the Vehicle Operating Cost relationships from webTAG.

C.1 Economic cost of accidents and casualties

The figures from webTAG relate to 2007 values and have been increased by the growth in GDP per capita (estimated as 2.5% per year), as recommended by the specification, to bring to 2010 figures. The costs are shown in Table C.1.

Table C.1 Costs of road accidents
Type of Accident Casualty Cost (£) Accident Cost (£)
Fatal 1,764,367 2,021,141
Serious injury 199,462 231,715
Slight injury 15,378 23,939
Average all accidents 56,914 81,424

C.2 Discount rate

The discount rate assumed in all analyses is the Treasury Test Discount Rate taken from the Department for Transport website and is 3.5% per year.

C.3 Traffic

The 2009 traffic flow data used in the analysis for this study is shown in Table C.2.

C.4 Traffic growth rate factors (NRTF)

Traffic growth rates used in the analysis were consistent with the Department for Transport National Road Transport Forecast (NRTF) (Department for Transport, 2011a) and are reproduced for the modelled years in Table C.3.

C.5 Value of Time

The values of time used in this study, shown in Table C.4, were taken from Department for Transport guidance (Department for Transport, 2011).

C.6 GDP deflator

Where cost data was not available in 2002 prices the costs were deflated to 2002 using the GDP deflator indices in Table C.5.

Table C.2 Traffic on Scottish local roads by vehicle type (2009)
Road Type Traffic (Million vehicle kilometres)
Cars 2 wheel motor vehicles Buses Light Goods Vehicles (LGV) Heavy Goods Vehicles (HGV) All motor vehicles
Major local roads
Non-trunk A roads - urban1 3,747 21 86 503 153 4,510
Non-trunk A roads - rural1 6,184 74 99 1,068 443 7,868
All major local roads 9,931 95 185 1,571 596 12,378
Minor roads (B, C and Unclassified)
Urban roads1 6,662 66 216 1,024 132 8,100
Rural roads1 5,233 59 90 1,319 215 6,916
All minor local roads 11,895 125 306 2,343 347 15,016
All local roads
Urban roads1 10,409 87 302 1,527 285 12,610
Rural roads1 11,417 133 189 2,387 658 14,784
All local roads 21,826 220 491 3,914 943 27,394

Note: 1. Scottish Transport Statistics uses the Department for Transport classification of urban and rural roads which is based on population. The classification used here is based on built up/non-built up areas.

Table C.3 Traffic growth rate factors from NRTF*
Year Car LGV PSV HGV
2009 1 1 1 1
2010 1.014600 1.021700 1.006900 1.024400
2013 1.057812 1.092228 1.029521 1.102951
2017 1.113016 1.194830 1.062652 1.216857
2020 1.147082 1.275811 1.090629 1.306208
2025 1.190979 1.414822 1.143427 1.463062
2030 1.231660 1.556266 1.204254 1.627888

* National Road Traffic Forecast

Table C.4 Value of time for each vehicle type
Year Car Van PSV 3 axle Truck Artic
2011 8.71 9.66 59.43 8.47 8.47
2012 8.78 9.75 59.89 8.55 8.55
2013 8.91 9.92 60.75 8.70 8.70
2014 9.07 10.13 61.82 8.89 8.89
2015 9.23 10.35 62.91 9.09 9.09
2016 9.39 10.56 63.98 9.28 9.28
2017 9.55 10.77 65.03 9.47 9.47
2018 9.69 10.95 65.91 9.62 9.62
2019 9.82 11.13 66.80 9.79 9.79
2020 9.96 11.31 67.70 9.95 9.95
2021 10.09 11.49 68.62 10.12 10.12
2022 10.23 11.68 69.54 10.28 10.28
2023 10.37 11.87 70.48 10.46 10.46
2024 10.52 12.07 71.43 10.63 10.63
2025 10.66 12.26 72.40 10.81 10.81
2026 10.81 12.46 73.37 10.99 10.99
2027 10.96 12.67 74.36 11.17 11.17
2028 11.11 12.87 75.37 11.36 11.36
2029 11.27 13.08 76.38 11.55 11.55
2030 11.42 13.30 77.41 11.74 11.74

C.7 Longitudinal Profile Variance (3m)

A conversion of IRI to 3m LPV has been adopted based on a preliminary analysis of the FILTER experiment correlating various profile measurements (Alonso, 2001). This is shown in Equation A1.

LPV = 0.2117 IRI1.8507 (A1)
Where
LPV is the 3m longitudinal profile variance (mm2)
IRI is the International Roughness Index (m/km)

C.8 Carbon costs

In calculating the costs of vehicle emissions from the emissions results from the HDM-4 analyses the central non-traded price of carbon was used from webTAG (Department for Transport, 2011a) as shown in Table C.6.

Table C.5 GDP deflator indices
Year GDP deflator at market prices GDP
(£m)
2010 = 100 Per cent change on previous year
2002 81.274 3.10 1,075,564
2003 83.771 3.07 1,139,744
2004 85.883 2.52 1,202,956
2005 87.627 2.03 1,254,058
2006 90.301 3.05 1,328,363
2007 93.004 2.99 1,404,845
2008 95.763 2.97 1,445,580
2009 97.147 1.45 1,394,989
2010 100.000 2.94 1,455,397
2011 103.000 3.0 1,526,000
2012 105.472 2.4 1,603,000
2013 108.320 2.7 1,694,000
2014 111.244 2.7 1,789,000
2015 114.248 2.7 1,889,000

C.9 Analyses driven by surface condition

The analysis assumes that the traffic flow in veh. km is distributed evenly over the road network.

The analysis did not include any consideration of the quality of the carriageway condition data provided by WDM (based on SCANNER network surveys). For this reason a maximum IRI value of 10 was set and any lengths with an IRI >=10 were deemed to have an IRI of 10.

C.10 Analyses of delays and emissions through roadwork sites

When developing the input data for the QUADRO analyses for road classes with both dual and single carriageway roads, the carriageway traffic flows for both single and dual carriageways were set to the same average flow for that road type.

Notional works lengths of 250m for single carriageways and 1000m for dual carriageways were chosen for the QUADRO analyses.

In determining the length of maintenance carried out the total length of maintenance over each 3, 4 or 5 year time interval was divided by the number of years in the time interval to obtain a treatment length per year. In the analysis, time intervals between 2020 to 2025 and 2025 to 2030 budgets for Scenarios 2 and 3 increase linearly. Therefore, in practice, the amount of maintenance would also have increased linearly over these intervals. However this simplification to a fixed average length maintained per year was considered sufficient for these analyses and required no further assumptions to be made on the amount of maintenance being carried out over the intervals of increasing budget.

Table C.6 Central non-traded price of carbon (2002 prices)
Carbon Costs Central Non-Traded Price
Year (£/Tonne)
2011 158.87
2012 161.25
2013 163.67
2014 166.13
2015 168.62
2016 171.15
2017 173.71
2018 176.32
2019 178.97
2020 181.65
2021 184.68
2022 187.70
2023 190.73
2024 193.76
2025 196.79
2026 199.81
2027 202.84
2028 205.87
2029 208.90
2030 211.92

C.11 Local Authority network lengths

Network carriageway length data for each Local Authority (based on data from the SRMCS 2008/10 report) is shown in Table C.7.

C.12 Local Authority budgets

The annual carriageway maintenance budgets, supplied by SCOTS, used by WDM for the 8 sample Authorities in the condition projection modelling and those used in the scaling up for the non-sample Authorities are shown in Table C.8 in 2010 prices.

Table C.7 Network length for Scottish local roads
Area Network Length (Carriageway km)
Urban Rural
A B C U A B C U
Aberdeenshire 62 65 50 616 625 736 1,486 1,780
Dumfries and Galloway 68 55 85 402 427 679 1,091 1,334
Edinburgh, City of 127 43 101 1,019 39 11 18 20
Fife 87 79 74 1,137 261 259 218 271
Glasgow City 174 72 243 1,275 0 0 0 0
Highland 74 91 97 756 1,314 888 1,341 2,178
North Lanarkshire 66 68 113 965 64 65 117 70
South Ayrshire 32 23 25 333 83 183 207 271
Rural 40 25 33 291 154 230 451 548
Rural 71 37 33 254 479 582 398 456
Rural 38 31 24 254 430 560 744 869
Rural 23 20 28 261 135 271 338 432
Rural 55 33 24 380 379 333 614 608
Urban 17 11 16 138 35 23 13 17
Urban 25 20 18 327 29 29 18 36
Urban 26 19 50 257 7 31 33 33
Urban 57 46 19 526 55 45 96 61
Urban 11 6 32 230 13 16 22 32
Urban 38 26 55 483 36 19 60 74
Urban 33 10 12 237 23 0 15 14
Semi Urban 25 46 21 327 97 150 190 263
Semi Urban 33 35 16 230 63 134 207 199
Semi Urban 19 20 20 251 69 76 81 98
Semi Urban 37 46 25 446 64 109 182 116
Semi Urban 75 61 77 872 202 182 359 369
Semi Urban 46 25 23 256 170 136 148 187
Semi Urban 33 45 16 492 128 73 100 88
City 65 29 40 642 12 17 53 53
City 44 12 94 346 4 3 26 15
Islands 20 7 6 82 141 198 154 370
Islands 13 5 23 81 212 157 176 379
Islands 47 16 31 41 285 166 143 461
TOTAL 1,578 1,126 1,522 14,206 6,033 6,359 9,097 11,702

 

Table C.8 Maintenance budgets used in condition modelling and scaling
Authority 2010 Budgets
Current
(£) 		20% Cut
(£) 		40% Cut
(£)
Aberdeenshire 9,737,910 7,790,328 5,842,746
Dumfries and Galloway 6,293,000 5,034,400 3,775,800
Edinburgh, City of 7,105,000 5,684,000 4,263,000
Fife 9,887,115 7,909,692 5,932,269
Glasgow City 2,908,990 2,327,192 1,745,394
Highland 7,493,745 5,994,996 4,496,247
North Lanarkshire 3,045,000 2,436,000 1,827,000
South Ayrshire 1,292,095 1,033,676 775,257
Rural 3,451,000 2,760,800 2,070,600
Rural 6,617,800 5,294,240 3,970,680
Rural 1,624,000 1,299,200 974,400
Rural 2,588,250 2,070,600 1,552,950
Rural 4,669,000 3,735,200 2,801,400
Urban 908,425 726,740 545,055
Urban 2,427,880 1,942,304 1,456,728
Urban 1,538,740 1,230,992 923,244
Urban 1,511,132 1,208,906 906,679
Urban 954,100 763,280 572,460
Urban 2,436,000 1,948,800 1,461,600
Urban 1,725,500 1,380,400 1,035,300
Semi Urban 2,126,425 1,701,140 1,275,855
Semi Urban 3,024,700 2,419,760 1,814,820
Semi Urban 1,618,925 1,295,140 971,355
Semi Urban 2,624,421 2,099,536 1,574,652
Semi Urban 21,755,510 17,404,408 13,053,306
Semi Urban 3,940,230 3,152,184 2,364,138
Semi Urban 2,664,375 2,131,500 1,598,625
City 406,000 324,800 243,600
City 1,294,548 1,035,639 776,729
Islands 1,492,050 1,193,640 895,230
Islands 1,799,464 1,439,571 1,079,678
Islands 3,316,850 2,653,480 1,990,110
TOTAL 124,278,180 99,422,544 74,566,908

Source: SCOTS