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

12 Scaling-up to the Full Network

12.1 Overall approach

To understand the effects of reductions in maintenance funding for local roads it was not possible in this study to analyse the whole network. The approach was therefore based on the analysis of the road networks in 8 sample Local Authorities to represent the national network. The results from the analysis of the 8 Authorities were scaled to represent the national network.

Some of the effects of changes in maintenance funding (e.g. vehicle operating costs) are driven by the condition of the road network and the traffic using the network, while others (e.g. costs of delays to traffic due to roadworks) are driven by the amount of maintenance undertaken on the network and the level of traffic. Each aspect of cost was therefore scaled independently and the scaled costs combined to show the overall costs for the network.

For all aspects of costs, the Local Authorities are considered in the groups shown in Appendix C (i.e. rural, urban, semi-urban, city). Each type of Authority is represented in the 8 sample Authorities and the results of the analyses for each Authority type were used to scale up the costs for the Authorities of that type that were not included in the sample Authorities.

Where the 8 sample Authorities included more than one Authority for an Authority type (e.g. there were 3 rural Authorities in the sample). The results from all the sample Authorities of the type were combined for use in estimating the costs for the Authorities of that type, not in the sample. The approach adopted for scaling up the results was the same for all Authority types but the analysis was carried out separately for each Authority type.

Where there was more than one sample Authority of the same type, the results from the analyses of the sample Authorities of that type were combined to create a representative factor that could be used to scale up the costs for the Authorities of that type, not included in the sample Authorities.

12.2 Representative factors

For each aspect of cost (e.g. vehicle operating cost) and the network and vehicle type considered, a representative factor for each Authority type was derived based on the sample Authorities of that type. These factors were used to convert the total costs for the sample Authorities of that type to a 'fingerprint' value for that aspect of cost to be used for all Authorities of that type not in the sample. The equivalent factor for each Authority not in the sample was then calculated and used to derive the value for each aspect of cost for each Authority.

Where the sample Authorities included more than one Authority of the same type, the results from the sample Authorities were used in the total cost for the network, not costs derived using the representative factors for that Authority type.

The relationship for the change in vehicle speed as roads deteriorate was based on a study of the change in traffic speed on trunk roads in England. This cost was therefore estimated only for urban and rural local A roads and the results from the sample Authorities were scaled only for these road types. No costs or benefits were estimated for changes in traffic speed due to road surface condition on other road types.

12.3 Total network cost

The total cost for the network was the sum of each of the costs for all road types and vehicle types in all Authorities. A description of the calculations applied to the sample analyses for each aspect of cost is given in Appendix L. The results from the application of the scaling methodology are shown in Table 12.1 to Table 12.3 in undiscounted 2002 prices for each budget scenario. The sample Authorities are highlighted in light blue.

Table 12.1 Costs for all the network for Scenario 1
Authority Vehicle Operating Costs (£m) Travel Time Delay Costs (£m) User Delay Costs (£m) CO2 Emissions Cost (Network Condition) (£m) Delay Carbon Costs (£m) Works Carbon Cost (£m) Baselined Cumulative Depreciation (£m)
Aberdeenshire 8374 39 24 455 0 5 68
Dumfries and Galloway 3149 21 10 171 0 6 31
Edinburgh, City of 9610 47 206 513 5 3 17
Fife 8682 48 60 474 1 5 1
Glasgow City 6297 49 16 323 0 1 67
Highland 4719 29 8 258 0 4 94
North Lanarkshire 8016 33 30 423 0 2 17
South Ayrshire 2667 15 3 140 0 1 28
Rural 22775 146 198 1244 1 17 16
Rural 41175 302 59 2297 0 12 93
Rural 41398 358 92 2334 0 12 37
Rural 23823 128 23 1281 0 2 38
Rural 22489 149 110 1236 1 12 16
Urban 5570 17 27 289 0 1 3
Urban 11285 50 68 593 0 2 9
Urban 13200 44 106 687 0 1 9
Urban 7846 23 18 405 0 0 12
Urban 13929 68 75 737 0 1 6
Urban 8583 27 45 447 0 1 13
Urban 7608 20 75 395 0 2 4
Urban 10392 67 37 572 0 1 12
Semi Urban 4880 22 74 261 0 2 4
Semi Urban 6344 36 54 344 0 2 3
Semi Urban 13838 110 47 775 0 1 13
Semi Urban 6754 45 185 368 1 5 15
Semi Urban 8570 46 50 461 0 2 10
Semi Urban 8708 27 100 463 0 4 4
Semi Urban 12048 73 17 621 0 0 25
City 7624 42 110 392 1 1 9
City 24847 196 67 1396 0 10 33
Islands 6609 36 37 359 0 4 7
Islands 10215 41 42 544 0 4 12
Islands 392020 2352 2073 21258 16 124 727
Total 8374 39 24 455 0 5 68

Note: (2002 prices undiscounted)

Table 12.2 Costs for all the network for Scenario 2
Authority Vehicle Operating Costs (£m) Travel Time Delay Costs (£m) User Delay Costs (£m) CO2 Emissions Cost (Network Condition) (£m) Delay Carbon Costs (£m) Works Carbon Cost (£m) Baselined Cumulative Depreciation (£m)
Aberdeenshire 8413 40 19 455 0 1 76
Dumfries and Galloway 3173 22 8 171 0 2 45
Edinburgh, City of 9675 51 176 514 2 1 22
Fife 8760 52 47 475 0 1 9
Glasgow City 6327 50 13 323 0 0 71
Highland 4739 30 6 258 0 1 103
North Lanarkshire 8067 35 24 424 0 0 19
South Ayrshire 2676 15 3 140 0 0 30
Rural 22892 152 154 1245 1 13 18
Rural 41368 314 46 2300 0 9 109
Rural 41585 372 72 2337 0 9 42
Rural 23949 133 18 1282 0 2 45
Rural 22600 155 86 1237 0 9 18
Urban 5604 18 22 290 0 1 4
Urban 11354 53 55 594 0 1 10
Urban 13289 46 87 689 0 1 11
Urban 7891 24 14 405 0 0 13
Urban 14019 72 62 739 0 1 7
Urban 8639 28 35 448 0 1 15
Urban 7658 21 61 395 0 2 5
Semi Urban 10468 72 29 573 0 1 15
Semi Urban 4921 24 60 261 0 2 6
Semi Urban 6394 38 42 345 0 1 4
Semi Urban 13934 117 37 776 0 1 17
Semi Urban 6804 48 142 369 1 4 20
Semi Urban 8637 49 39 462 0 2 13
Semi Urban 8776 29 74 464 0 3 5
City 12130 78 14 622 0 0 27
City 7677 45 91 392 1 1 10
Islands 24958 204 53 1397 0 8 37
Islands 6642 38 29 359 0 3 8
Islands 10270 42 34 545 0 4 14
Total 394292 2469 1650 21289 9 86 845

Note: (2002 prices undiscounted)

Table 12.3 Costs for all the network for Scenario 3
Authority Vehicle Operating Costs (£m) Travel Time Delay Costs (£m) User Delay Costs (£m) CO2 Emissions Cost (Network Condition) (£m) Delay Carbon Costs (£m) Works Carbon Cost (£m) Baselined Cumulative Depreciation (£m)
Aberdeenshire 8454 42 13 456 0 1 87
Dumfries and Galloway 3195 23 6 171 0 1 54
Edinburgh, City of 9739 56 141 514 1 1 26
Fife 8835 56 32 476 0 1 18
Glasgow City 6349 52 9 324 0 0 73
Highland 4761 31 4 259 0 1 113
North Lanarkshire 8121 37 18 424 0 0 21
South Ayrshire 2686 16 2 140 0 0 32
Rural 23013 159 112 1247 1 10 21
Rural 41573 327 33 2303 0 7 121
Rural 41786 388 52 2340 0 7 46
Rural 24078 139 13 1284 0 1 50
Rural 22716 161 62 1239 0 7 21
Urban 5640 19 16 290 0 1 4
Urban 11427 55 42 595 0 1 12
Urban 13382 49 65 690 0 1 12
Urban 7937 25 11 406 0 0 15
Urban 14114 76 48 740 0 1 8
Urban 8699 30 27 449 0 0 17
Urban 7710 22 46 396 0 1 5
Semi Urban 10541 77 21 575 0 1 18
Semi Urban 4963 25 43 262 0 1 7
Semi Urban 6441 41 29 345 0 1 5
Semi Urban 14022 125 26 777 0 1 21
Semi Urban 6852 51 99 370 1 3 25
Semi Urban 8702 52 27 463 0 1 16
Semi Urban 8834 31 48 465 0 2 7
City 12203 84 11 623 0 0 29
City 7722 48 69 393 1 1 10
Islands 25077 212 38 1399 0 6 41
Islands 6677 39 22 360 0 2 9
Islands 10326 44 25 546 0 3 16
Total 396577 2592 1212 21321 7 62 961

Note: (2002 prices undiscounted)