Chapter 4 - Road network

Introduction

This chapter provides information about public road lengths by local authority, road class, type and speed limit. It also includes statistics on the amount of trunk road constructed/re-surfaced and information on the residual life of the trunk road network.

Unusual year to year changes in the reported road lengths may be due to the gradual introduction of Geographical Information Systems (GIS) to calculate road lengths by the data providers - see road network section of the user guide.

Key Points

• Scotland has 57,187 km of road network.
• Seven per cent is trunk road (1% is motorway).
• Scotland has 10.4 km of road per 1,000 people compared to 6.0 km in GB.

Main Points

Road length

There were 57,187 kilometres of public road in Scotland at 31 March 2022. The trunk road network accounted for 7% of the total. Other (non-trunk) A roads represented 13% of the total. Minor roads (B and C roads, and unclassified roads) accounted for the remaining 80% of roads. (Table 4.1)

There was little change in the length of the motorway between April 2021 and April 2022. (Table 4.1)

Over a quarter of the total trunk road network, and about one-seventh of the Scottish road network, is within the area of the Highland Council. Around 10% of the Scottish road network is within the Aberdeenshire Council area and a further 8% is within the Dumfries and Galloway Council area. These three local authorities account for almost a third of Scotland’s road network. (Table 4.2)

Road Maintenance

Overall there was a decrease of 44% in the amount of trunk road that was newly constructed, reconstructed, strengthened or surface dressed in 2022-23 compared to the previous year. (Table 4.3)

In 2022-23, 16.4% of the motorway network, 13.6% of the dual carriageway and 13.9% of the single carriageway trunk road network required close monitoring of the state of the road surface. (Table 4.5 (b))

In 2022-23 the National Road Condition Indicator (RCI) showed 27% of the local authority A road network may, following more detailed examination, require some kind of maintenance (see the road network section of the user guide. For the whole of the local authority network (all road categories), about 33% may similarly require some kind of maintenance. (Table 4.6)

---

Notes

Note 1

Motorway road lengths are derived from GIS from 2000 onwards - see commentary for more details.

Note 2

Road lengths are physical length rather than carriageway length e.g. 10km of dual carriageway counts as 10km, not 20km.

Note 3

These figures now include A road slip roads which have been excluded from the figures in previous publications. The time series has been updated to include this data resulting in an increase of 3-4% in Trunk road length and an increase in overall road length of 0.2%. The methodology for calculating the trunk road totals from the database has also changed resulting in some small changes to road lengths from those previously published.

Note 4

Trunk road lengths for these roads have now been derived more accurately using a GIS system from 2006.

Note 5

For 2008 and 2009 single and dual carriageways figures are estimated.

Note 6

As at 30 May 2014.

Note 7

Local authority road lengths at the end of the financial year e.g. 2013=2013/14.

Note 8

Motorway road lengths have been consolidated using a GIS system which means that there will be some changes to previously published figures.

Note 9

Triangulation with other sources of road length data has occurred to improve the quality of the information. Figures may not be comparable with previous editions.

Note 10

The drop in the length of trunk A roads from last year is probably due to the detrunking of A80 with the opening of the M80.

Note 11

Local authority road lengths at the end of the financial year.

Note 12

FBOC records are now incorporated into South East following the introduction of the Newtork Maintenance Contracts, August 2020

Note 13

Residual life represents the number of years to elapse before the pavement reaches the stage when it may be necessary to undertake relatively more expensive reconstruction rather than strengthening to restore its full life.

Note 14

Method of calculation changed in 2011-12.

Note 15

The part of the network that requires close monitoring is that which has a residual life of less than zero. Note: it has been decided that surveyed network length is not required as the figures produced are now representative of the whole network as shown in Table 4.1.

Note 16

These figures are provisional.

Note 17

FBOC records are now incorporated into South East following the introduction of the Newtork Maintenance Contracts, August 2020

Note 18

From 2007-08 the basis of the statutory road performance indicator in Scotland changed to the UK Standard Road Condition Indicator.

Note 19

While it has been possible, following the change to the indicator, to calculate the equivalent RCI value for all classified roads from 2005-06, it has not been possible to do this in a reliable manner for unclassified roads, owing to a lack of cracking data for those years. As unclassified roads represent a significant part of the total road network, RCI data for the network is similarly not available for this period. It is important to note that owing to the different formulation, no valid comparison can or should be made between the two series.

Note 20

The categories used to indicate the condition of the road are in brief: amber - further investigation should be undertaken to establish if treatment is required. red - the road has deteriorated to the point at which it is likely repairs to prolong its future life should be undertaken.

Note 21

Information for 2002-03 is available only for A roads.

Note 22

The SPI figures for Scotland in 2004-05 exclude Glasgow, as the survey in Glasgow was undertaken on a different basis in that year.

Note 23

For 2020-21 a new filter was introduced in accordance with the revised standard ISO 13473-1. This has led to an increase in the recorded texture values of between 0.03 and 0.06mm, which in turn has resulted in a slight reduction in the reported red and amber values which make up the performance indicator.

Note 24

An error has recently been found in the way local authority dual and single carriageway A roads were calculated wherby dual carriageway A roads with parking restrictions were being included twice. Small revisions from 2012 onwards have been made. The overall total length of local authority A roads was unaffected.