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ROAD ACCIDENTS SCOTLAND 1999

Annex E
Local Government Reorganisation and the Trunk Road Network

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 back to 1981 for the areas covered by the new Councils 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 reference 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.

The Trunk Road Network

Trunk roads are those roads for whose upkeep the First Minister is 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.

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, a comparison of the numbers of accidents on trunk roads before and after 1st April 1996 would be misleading. Comparisons of figures for local authority roads could also be misleading, particularly when one looks 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.

A special exercise was required to obtain figures for several years for the numbers of accidents which occurred on the roads which form the new trunk road network. This involved identifying, from among the accidents which happened 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, (c) 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 (c) would show it as a trunk road for accidents before that date, and would show it as a local authority road thereafter.

Because figures are available for each year from 1992 to 1995 both on the basis of the old trunk road network and on the basis of the new trunk road network, a comparison of the 1992-95 figures on the two bases indicates 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 numbers of accidents on the local authority road network that was caused by the transfers. This information can be used to calculate percentage changes, between the 1981-85 annual averages and the latest figures, which are adjusted to take account (as best one can, from the information which is available) of the changes to the networks that took effect on 1st April 1996.

As an example of how the "adjusted" percentage changes are calculated, suppose that, in one case, the figures are:

then the percentage change between the 1981-85 and 1995-99 averages, adjusted for the change in the trunk road network, is calculated as follows:

Similarly, if the 1999 figure were 90, the adjusted percentage change from 1981-85 to 1999 would be:

100 * ( 90 - 58.33 ) / 58.33
or about 54%
(compared with an "unadjusted" figure of 80%)

It should be noted that this adjustment process does not adjust for 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)

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