Local Government Reorganisation and the Trunk Road Network
This Appendix explains how statistics for the areas of the new Councils were produced for the period prior to local government reorganisation on 1 April 1996. It then describes the trunk road network the changes made tit then, and their effect on the statistics. The next section is about identifying accidents which occurred prior to 1 April 1996 on the roads which formed the post- 1 April 1996 trunk road network, so that figures could be produced on a consistent basis pre- and post-1996. Subsequent sections explain how the effect of the change for individual Council areas can be assessed, how the 1994-98 averages for trunk roads and local authority roads were calculated, and how accident and casualty rates for 1995 and earlier years were calculated. The final section mentions how the statistics for some types of road in some areas may be affected by the opening of new roads.
2. Local Government re-organisation
The reorganisation of local government established new Councils with effect from 1st April 1996, to replace the former Regions, Districts and Island Areas. Statistics for the areas covered by the new Councils for earlier years (back to 1981) were derived in three ways:
a. in the case of the former Island Areas, by allocating all the accidents which occurred in each Island Area to the relevant Council.
b. in those cases where a whole District fell in a new Council's area, by allocating all the accidents which occurred in that District to the area of the new Council.
c. in the case of accidents occurring in the five Districts which had major parts falling in several new Councils' areas, by a special exercise, which used the grid co-ordinates recorded for each individual accident to allocate it to the area of one of the new Councils, using a computer mapping system. This was successful for 99% of accidents for these five Districts, consistently over all years from 1981. The remaining 1% of the accidents in the five Districts were assigned to the new Council in which the majority of the District's accidents fell. This should cause only a very small error (considerably less than 1%) for any of the new Councils, in any year.
3. The Trunk Road Network
Trunk roads are those roads for whose upkeep Scottish Ministers are responsible. The Government's view, when it reviewed the trunk road network in 1994, was that the trunk road network should:
a. provide the road user with a coherent and continuous system of routes which serve destinations of importance to industry, commerce, agriculture and tourism;
b. define nationally important routes which will be developed in line with strategic national transport demands; and
c. ensure that those roads which are of predominantly local importance are managed locally.
Currently, the trunk road network in Scotland consists of all the Motorways plus some (but not all) of the A roads. In some cases, the trunk road network may include the whole of a particular road; in other cases, only certain stretches of a road may be part of the trunk road network. For example, only that part of the A7 which runs south of the junction with the A6091 near Galashiels is part of the current trunk road network: the northern part is not a trunk road.
4. Changes to the trunk road network in April 1996, and their effect on the statistics
Following the review of the trunk road network, several changes were made with effect from 1st April 1996 (coinciding with the reorganisation of local government). Some roads (or stretches of road) which had previously been part of the trunk road network were transferred to local authority control: examples include the A7 from near Edinburgh to near Galashiels, and the A91 from the M90 to St Andrews. Some roads which had previously been the responsibility of local authorities became part of the new trunk road network: examples include the A720 Edinburgh City bypass east of the M8 extension and the A95 from Aviemore to Keith. The overall result was that, on 1st April 1996, about 214 miles of road ceased to be trunk road, and about 361 miles of road became trunk road.
Because of these changes to the trunk road network, the original figures for the numbers of accidents which occurred on trunk roads before and after 1st April 1996 were on different bases, and a comparison could be misleading. Comparisons of the figures for local authority roads could also be misleading, particularly when one looked at the figures for the areas covered by certain Councils, because they may relate to significantly different road networks before and after 1 April 1996.
5. Identifying accidents which occurred before April 1996 on the roads which formed the post- 1 April 1996 trunk road network, tenable comparison of the numbers before and after 1996
In order to get figures for some of the years before 1996 which were on the basis of the post- 1 April 1996 road network, a special exercise was undertaken. This identified, from among the accidents which took place between 1st January 1992 and 31st March 1996, those which occurred on the stretches of road which form the new trunk road network (i.e. the trunk road network that took effect from 1st April 1996). As a result, the information that is available in the Transport Statistics branch database enables figures to be produced for the numbers of road accidents on trunk roads, and on local authority roads, using the following definitions of the status of the road:
a. status at the time of the accident - these figures are available for all years
b. status in terms of the old network - available up to 31 March 1996 only
c. status in terms of the new network - available for all years from 1992
It should be noted that the definitions under (b) and (c) above should, strictly speaking, be expanded:
i. For accidents which occurred before 31st March 1996, (b) is actually the status at the time of the accident (rather than the status at 31 March 1996): the two will differ in the case of any roads whose status changed before 31 March 1996. For example, if a road ceased to be a trunk road on (say) 15 May 1994, then definition (b) would show it as a trunk road for accidents before that date, and would show it as a local authority road thereafter.
ii. For accidents which occurred after 1st April 1996, © is actually the status at the time of the accident (rather than the status at 1 April 1996): the two will differ in the case of any roads whose status changed after 1 April 1996. For example, if a road ceased to be a trunk road on (say) 8 July 1996, then definition © would show it as a trunk road for accidents before that date, and would show it as a local authority road thereafter.
6. Assessing the effect of the April 1996 changes on the figures for trunk roads and for local authority roads, for individual local authority areas
Because data for 1992 to 1995 are available both on the basis of the old trunk road network and on the basis of the new trunk road network, one can see the extent of the change in the number of accidents on the trunk road network that was caused by the transfer of roads (or stretches of roads) between the trunk road network and the local authority road network. Similarly, one can compare the figures on the two bases for the local authority road network to see the extent of the change in the total number of accidents on that network that was caused by the transfers.
1992-95 averages on both bases were included in, for example, Tables 4 and 40© of Road Accidents Scotland 2000. The figures in the first of these tables showed that the April 1996 changes had little effect on the trunk road network's overall share of the total number of accidents in Scotland as a whole. However, the figures in the second table showed that the changes did have a noticeable effect on the trunk road network's share in some parts of Scotland. For example, the 1992-95 annual average number of casualties, on all types of road, in the area which is now covered by Highland Council was 1,079. Of these, an average of 423 (39%) occurred on the roads which formed the pre- 1 April 1996 trunk road network, and 495 (46%) occurred on the roads which formed the post- 1 April 1996 trunk road network. Therefore, the April 1996 changes could have a noticeable effect on the 1994-98 averages for trunk roads and local authority major roads for some local authority areas.
7. How the statistics for some types of road in some areas may be affected by the opening of new roads
Finally, it should be noted that analysis by type of road does not take account of changes in the numbers of accidents which result from traffic transferring from one kind of road to another when a new road opens. For example, when a new road is built, the majority of the traffic which uses it may be traffic that previously used another road. In some cases (eg when a motorway is constructed to replace an existing trunk road) the original road which carried the traffic may cease to be a trunk road when the new road opens, because the new road replaces it as a trunk road. However, the records of the accidents which occurred on the original road will continue to show that they occurred on the original road: they will not be amended to be counted against the new road. In such a case, when the statistics are analysed on the basis of the new networks, those accidents which occurred on the original road will be counted as occurring on what is now part of the new local authority road network, and those accidents which occurred on the new road will be counted as occurring on the new trunk road network. When one looks at series of figures for the new networks for a number of years, which span the year of the change, the figures for the new local authority network would fall, and the figures for the new trunk road network might rise, in the year in which the new road was opened, because of the transfer of traffic from the original road (which was a trunk road then, but is now part of the local authority road network) to the new road (which is part of the new trunk road network).