10. Sources and definitions
10.1 The sources of the data
The figures in this bulletin were compiled from the "Stats 19" statistical returns made by police forces. These 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. As noted in section 2.2, there could be many non-fatal injury accidents which are not reported by the public to the police, and are therefore not counted in these statistics because the police can only include in their returns details of the accidents of which they are aware. More information about this is given in Reported Road Casualties Scotland 2010, in the section entitled Estimating under-counting of Road Casualties in Scotland. The vehicle(s) involved in the accident need not be moving, and need not be in collision - for example, the returns include accidents involving people alighting from buses. Damage only accidents (i.e. accidents which do not involve personal injury) are not included in these statistics. Transport Scotland are looking at alternative data sources to estimate the levels of under reporting.
Data used in this publication was extracted from Transport Scotland's reported road accident statistical database in May 2013. The figures published here are marked as provisional as late returns and amendments will be included in the final figures published in Reported Road Casualties Scotland in October and in figures included in later years publications.
The differences between the provisional and final numbers are likely to be small. The figures for previous years are included in the table below. Over the last three years, there has been no difference in the number of people killed between the June and October publications. The figure published in Reported Road Casualties Scotland has been 0.1% higher for Serious and Slight casualties and all severities. Differences may be larger for some subsets of the data, for example the tables by mode, so small changes should be treated with caution.
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10.3 The definition of "severity" used in the Road Accident statistics
The classification of the severity of an accident (as "fatal", "serious" or "slight") is determined by the severity of the injury to the most severely injured casualty. The police usually record this information soon after the accident occurs. However, if further information becomes available which would alter the classification (for example, if a person dies within 30 days of the accident, as a result of the injuries sustained in the accident) the police change the initial classification of the 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 (e.g. on the fitting and wearing of seat belts), will all have 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, people may suffer only "slight injury" in collisions that previously would have taken place at higher speeds and so might previously have resulted in "serious injury".
However, it is also possible that some of the changes shown in the statistics of "serious injuries" and "slight injuries" may be due to changes in administrative practices, which may have altered the proportion of accidents categorised as "serious". For example, the distinction between "serious" and "slight" injuries could be affected by factors such as changes in hospitals' admission policies. 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. The increase in the number of "serious" injury accidents in 1994 was partly attributed to a change in the health boards' policies in admitting more child casualties for overnight observation, which in turn changed the classification of many injuries from "slight" to "serious". The number of child casualties recorded as having serious injuries in 1994 was 35 per cent higher than in the previous year. 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.
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).
Children: people under 16 years old.
Pedestrians: includes people riding toy cycles on the footway, people pushing bicycles, occupants of prams or wheelchairs, and people who alight safely from vehicles and are subsequently injured.
10.5 Scottish specific casualty reduction
Scotland's Road Safety Framework was launched in June 2009. It set out the vision for road safety in Scotland, the main priorities and issues and included Scotland-specific targets and milestones which will be adopted from 2010. These targets and milestones are:
|Target||2015 milestone % reduction||2020 target % reduction|
|People seriously injured||43%||55%|
|Children (aged < 16) killed *||35%||50%|
|Children (aged < 16) seriously injured||50%||65%|
* As numbers are small, a 3 year average is included in the table to smooth out large fluctuations in the numbers.
Each reduction target will be assessed against the 2004/08 average. In addition to the targets a 10 per cent reduction target in the slight casualty rate will continue to be adopted.
The 4 main targets differ to previous targets in that deaths have been separated out from serious injuries as, in recent years, trends have been different - serious injuries falling steadily but deaths declining at a lower rate. These targets will be discussed more in future publications.
10.6 The calculation of the "indicative lines" shown in the graphs
One way of assessing progress towards the targets is to compare actual casualty numbers in each year with an indicative line that starts at the baseline figure in 2006 and falls, by a constant percentage reduction in each subsequent year, to the target for 2010. This is the approach adopted by the GB Road Safety Advisory Panel. The indicative line starts at the baseline figure in 2006 as that is the middle year of the baseline period. Other approaches could have been used: there are many ways of producing lines that indicate how casualty numbers might fall fairly steadily to the targets for 2020.
The method adopted to produce the indicative target lines shown in Figure 4 involves a constant percentage reduction in each year after 2006 to the 2015 milestone, then a constant percentage reduction between 2015 and 2020. The resulting indicative target lines represent the percentages of the baseline averages which are shown in the table below. They are not straight lines, because of the compounding over the years effect of constant annual percentage reductions (to two decimal places, the falls are: 3.89 per cent p.a. for killed to meet the 2015 milestone and 3.02 between 2015 and 2020. For seriously injured casualties the falls are 6.06 per cent and 4.61 per cent. For child killed 4.67 per cent and 4.37 or seriously injured 7.41 per cent and 6.90.
|Killed||Serious||Child killed||Child serious|
|% baseline (milestone from 2015)||% reduction from baseline (milestone)||% baseline (milestone from 2015)||% reduction from baseline (milestone)||% baseline (milestone from 2015)||% reduction from baseline (milestone)||% baseline (milestone from 2015)||% reduction from baseline (milestone)|