Economic, Environmental and Social Impacts of Changes in Maintenance Spend on the Scottish Trunk Road Network

Appendix D Summary of key data and assumptions

D.1 Traffic data

For this analysis, the traffic carried by the trunk road network was derived from the data extracted from the Transport Scotland asset database for 2008 and is summarised in Table D.1.

Table D.1 Annual total vehicle km travelled by road type and vehicle type (2008)

Vehicle Type

Traffic (Vehicle kilometres)

Motorway

Dual

Single

All

Car

4,769,787,191

5,416,703,223

5,804,398,697

15,990,889,112

LGV

657,082,076

434,925,796

382,040,517

1,474,048,391

PSV

133,969,557

88,766,829

78,087,386

300,823,773

OGV1

161,215,253

106,710,352

93,868,098

361,793,704

OGV2

561,990,914

371,913,699

326,848,004

1,260,752,618

Total Heavy Vehicles

857,175,724

567,390,880

498,803,488

1,923,370,095

Traffic growth rates used in the analysis were consistent with the National Road Transport Forecast (NRTF) given by STAG (Transport Scotland, 2011b) (Transport Scotland, 2011b) and (Department for Transport, 2011) and are reproduced for the modelled years in Table D.2.

Table D.2 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

Summarising the data by Light and Heavy Goods Vehicles (including PSVs) allowed the percentage of HGVs to be calculated for each road type, shown in Table D.3.

Table D.3 Percentage of HGV by road type

Road Type

HGV

Motorway

24%

Dual APTR

15%

Single APTR

13%

D.2 GDP deflator

Where cost data was not available in 2002 prices the costs were deflated to 2002 using the GDP deflator indices in Table D.4 taken from STAG (Transport Scotland, 2011b) (Transport Scotland, 2011b) and webtag guidance (Department for Transport, 2011).

Table D.4 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

D.3 Fuel Efficiency Improvements

The engine fuel efficiency factors used in this study, shown in Table D.5, were taken from STAG (Transport Scotland, 2011b) (Transport Scotland, 2011b) and webtag guidance (Department for Transport, 2011).

Table D.5 Engine fuel efficiency factors

Year

Average Car

Average LGV

PSV

3 axle Truck

Artic

2010-2015

-1.87

-1.72

0

0

0

2015-2020

-2.71

-1.7

0

0

0

2020-2025

-3.13

-0.96

0

0

0

2025-2030

-2.33

-0.26

0

0

0

D.4 Increase in cost of fuel

Factors for the increase in fuel costs used in this study, shown in Table D.6, were taken from STAG (Transport Scotland, 2011b) (Transport Scotland, 2011b) and webtag guidance (Department for Transport, 2011).

Table D.6 Increase in fuel costs

Year

Average Car

Average LGV

2020-2025

0.99

1.02

2025-2030

0.95

0.96

D.5 Economic cost of accidents and casualties

The costs of accidents from the STAG and (Transport Scotland, 2011b) (Transport Scotland, 2011b) webTAG guidance (Department for Transport, 2011) relate to 2007 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 D.7.

Table D.7 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

D.6 Discount rate

The annual discount rate assumed in all analyses is the Treasury Test Discount Rate taken from the Scottish Transport Statistics website and is 3.5%.

D.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 D1.

LPV = 0.2117 IRI1.8507 (D1)

Where LPV is the 3m Longitudinal Profile Variance (mm2)

IRI is the International Roughness Index (m/km)