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8.1 The sources of the data
The statistics in this bulletin were compiled from returns made by police forces, which cover all accidents in which a vehicle is involved that occur on roads (including footways) and result in personal injury, if they become known to the police. The vehicle need not be moving, and need not be in collision - for example, the returns include accidents involving people alighting from buses. "Damage only" accidents are not included in this definition.
8.2 The definition of "severity"
For the purposes of the Road Accidents statistical returns:
a fatal injury is one which causes death less than 30 days after the accident;
a fatal accident is an accident in which at least one person is fatally injured;
a serious injury is one which does not cause death less than 30 days after the accident, and which is in one (or more) of the following categories:
(a) an injury for which a person is detained in hospital as an in-patient
or (b) any of the following injuries (whether or not the person is detained in hospital): fractures, concussion, internal injuries, crushings, severe cuts and lacerations, severe general shock requiring treatment
or (c) any injury causing death 30 or more days after the accident;
a serious accident is one in which at least one person is seriously injured, but no-one suffers a fatal injury;
a "slight" injury is any injury which is neither "fatal" nor "serious" - for example, a sprain, bruise or cut which is not judged to be severe, or slight shock requiring roadside attention;
a "slight" accident is one in which at least one person suffers "slight" injuries, but no-one is seriously injured, or fatally injured;
Over the years, improvements in vehicle design, and the provision and use of additional safety features, together with changes in the law (eg on the fitting and wearing of seatbelts), will have all helped to reduce the severity of the injuries suffered in some accidents. Road safety measures should also have reduced the levels of injuries sustained - for example, if traffic calming schemes reduce average speeds and hence reduce the speeds at which collisions occur. In addition, the distinction between "serious" and "slight" injuries could be affected by factors such as changes in hospitals’ admission policies. For example, all else being equal, the number of "serious injury" cases would rise, and the number of "slight injury" cases would fall, if it became standard procedure for a hospital to keep in overnight, for precautionary reasons, casualties with a particular type of injury (section 2.3 of the 1995 bulletin explained that part of the increase in "serious injury" cases in 1994 was due to hospitals admitting more child casualties for overnight observation). There could also be changes in hospitals’ procedures that would reduce the numbers of "serious injury" cases. In addition, there is anecdotal evidence that changes in procedures for assigning severity codes may affect the categorisation of injuries. For example, different severity codes might be assigned by a police officer who was at the scene of an accident and by a clerk who bases the code on a police officer’s written description of the accident. Therefore, it is possible that some of the changes shown in the figures for "serious injuries" and "slight injuries" may be affected by changes in administrative practices, which may have altered the proportion of accidents which is categorised as "serious".
8.3 Some other definitions
Built-up roads: accidents which occur on "built-up" roads are those which occur on roads which have speed limits of up to 40 miles per hour (ignoring temporary speed limits on roads for which the normal speed limit is over 40mph). Therefore, an accident on a motorway in an urban area would not be counted as occurring on a "built-up" road, because the speed limit on the motorway is 70mph. An accident on a stretch of motorway with a temporary speed limit of 30mph would not be counted as occurring on a "built-up" road, because the normal speed limit is 70mph.
Children: people under 16 years old.
Pedestrians: includes people riding toy cycles on the footway; people pushing or pulling bicycles or other vehicles; people leading or herding animals; occupants of prams or wheelchairs; people who alight safely from vehicles and are subsequently injured.
8.4 The calculation of the "target lines" shown in the graphs
In each graph, the faint dotted line shows how the numbers of casualties could have fallen, had there been a constant percentage reduction each year, from the actual number in 1987 (the year of adopting the target) to the year 2000 target of one-third of the 1981-85 average.
These "target lines" were not straight lines, because each year’s fall was calculated by applying a constant percentage reduction to the target line’s number of casualties in the previous year (which reduced each year). The total number of casualties in the year 2000 would have been two-thirds of the 1981-85 average level if there had been a constant reduction of about 2.38% (compound) each year after 1987. The calculation of the 2.38% was as follows:
| 1981-85 average total number of casualties | 27,142 | |
|
1987 total number of casualties | 24,748 | |
|
Target for year 2000 (two-thirds of 1981-85 average) |
18,095 | |
|
Percentage of number in 1987 | 73.1% | |
| Percentage reduction required from 1987 to 2000 | 26.9% | |
|
Implied annual percentage reduction in each of 13 years |
2.38% (compound) |
The "target line" figure for each year was calculated in a way which is best described by giving the example of the calculation of the target line figure for 1999. As that year was twelve years after 1987, the 1999 "target line" figure was found by applying a compound reduction of 2.38% per year for twelve years to the 1987 figure of 24,748. The result was a 1999 "target line" figure of 18,536, which was 31.7% below the 1981-85 average of 27,142.
Repeating these calculations for the different types of casualty gave different annual percentage reductions. This is because, in each case, the 1987 actual figure, which was the "starting position" for the line, represented a different percentage of the 1981-85 average level. It follows that one would have needed a different value for each type of casualty for the constant compound percentage reduction each year after 1987 in order for its year 2000 figure to have been two-thirds of the 1981-85 average level for that type of casualty.
8.5 The targets for reducing road accident casualties by the year 2010
On 1 March 2000, the UK Government, the Scottish Executive and the National Assembly for Wales announced a new road safety strategy and casualty reduction targets for 2010. The new targets, which were given in the document "Tomorrow's roads - safer for everyone", are based on the annual average casualty levels over the period 1994 to 1998, and are for:
Progress towards the new targets will be shown in subsequent editions of "Key Road Accident Statistics". The relevant casualty figures for 2001 onwards will be compared with indicative target lines which start at the actual figures for 2000 (because that was the year in which the new targets were adopted) and fall, by a constant percentage each year, to the target figures for the year 2010.
More detailed figures will be published in "Road Accidents Scotland". Table 44 of "Road Accidents Scotland 1999" showed the "baseline" 1994 to 1998 average figures for each local authority area for the first two targets, along with the corresponding figures for 1999. More statistics relating to the new targets will appear in subsequent editions of "Road Accidents Scotland".
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