Annex A: Supporting information including comparisons with other sources
Sources of the data
The figures in this bulletin were compiled from Stats 19 statistical returns made by Police Scotland. These returns cover all collisions in which a vehicle is involved that occur on roads (including footways) and that result in personal injury. Only injury collisions reported to the police are included. The vehicle(s) involved in the collision need not be moving, and need not be in collision—for example, the returns include collisions involving people alighting from buses. Damage-only collisions, in which no people are injured, are not included in these statistics.
There could be many non-fatal injury collisions which are not reported to the police, and as a result these statistics are expected to undercount the true number of road casualties.
Stats 19 forms and guidance are available on the Department for Transport website.
Provisional data
Data used in this publication were extracted from Transport Scotland’s reported road collision statistical database in May 2024. 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. Table 3 (overleaf) shows the difference between the provisional and final number of casualties. In most years, the difference between the provisional and final figures is less than 0.5%.
| Year | Killed | Seriously injured | Slightly injured | All severities | Killed (% dif) | Seriously injured (% dif) | Slightly injured (% dif) | All severities (% dif) |
|---|---|---|---|---|---|---|---|---|
| 2001 | 0 | 1 | 4 | 5 | N/A | 0.00% | 0.00% | 0.00% |
| 2002 | 1 | 9 | 0 | 10 | 0.30% | 0.30% | N/A | 0.10% |
| 2003 | -1 | 9 | 29 | 37 | -0.30% | 0.30% | 0.20% | 0.20% |
| 2004 | -1 | 30 | 130 | 159 | -0.30% | 1.10% | 0.80% | 0.90% |
| 2005 | 0 | 58 | -29 | 29 | N/A | 2.20% | -0.20% | 0.20% |
| 2006 | 0 | 31 | 159 | 190 | N/A | 1.20% | 1.10% | 1.10% |
| 2007 | -1 | 66 | 85 | 150 | -0.40% | 2.80% | 0.60% | 0.90% |
| 2008 | -2 | 33 | -18 | 13 | -0.70% | 1.30% | -0.10% | 0.10% |
| 2009 | 0 | 0 | 17 | 17 | N/A | N/A | 0.10% | 0.10% |
| 2010 | 0 | 4 | 6 | 10 | N/A | 0.20% | 0.10% | 0.10% |
| 2011 | 0 | 2 | 5 | 7 | N/A | 0.10% | 0.00% | 0.10% |
| 2012 | 4 | 15 | 82 | 101 | 2.30% | 0.80% | 0.80% | 0.80% |
| 2013 | 0 | 5 | 0 | 5 | N/A | 0.30% | N/A | 0.00% |
| 2014 | -3 | 5 | 23 | 28 | -1.50% | 0.30% | 0.20% | 0.20% |
| 2015 | 0 | -1 | 13 | 18 | N/A | -0.10% | 0.10% | 0.20% |
| 2016 | 0 | 4 | 16 | 20 | N/A | 0.20% | 0.20% | 0.20% |
| 2017 | 0 | 9 | 28 | 37 | N/A | 0.60% | 0.40% | 0.40% |
| 2018 | 1 | 1 | 7 | 9 | 0.60% | 0.10% | 0.10% | 0.10% |
| 2019 | -3 | 15 | 32 | 44 | -1.80% | 0.70% | 0.60% | 0.60% |
| 2020 | -1 | 8 | 41 | 48 | -0.70% | 0.50% | 1.20% | 1.00% |
| 2021 | 1 | 19 | 60 | 80 | 0.70% | 1.20% | 1.80% | 1.60% |
| 2022 | -1 | 17 | 18 | 34 | -0.60% | 1.00% | 0.50% | 0.60% |
Approach to evaluating progress against casualty reduction targets within this publication
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 2014-18 and falls, by a constant percentage reduction in each subsequent year, to the target for 2030. This is the approach previously adopted by the GB Road Safety Advisory Panel. The indicative line starts at the baseline figure in 2016 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 2030.
The method adopted to produce the indicative target lines shown in Figures 11, 12, 13 and 14 involves a constant percentage reduction in each year from 2016 to 2030. The resulting indicative target lines represent the percentages of the baseline averages. 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: 4.83% p.a. for killed and seriously injured to meet the 2030 target. For children killed and seriously injured the fall is 6.34% p.a..
The calculations themselves are contained within the spreadsheet accompanying this publication.
Severity reporting
The classification of the severity of an collision (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 collision occurs. However, if further information becomes available which would alter the classification (for example, if a person dies within 30 days of the collision, as a result of the injuries sustained in the collision) the police change the initial classification of the severity.
From the middle of 2019, Police Scotland have used the CRASH system for recording severity details of collisions. Table 4 lists the options for determining how severe an injury is. The introduction of CRASH means that the severity of injuries is recorded more accurately than before and has led to an increase in the recorded number of serious injuries. Figures recorded from 2019 onwards are therefore not directly comparable with those recorded prior to the introduction of CRASH. The adjustment methodology discussed in the Introduction is an attempt to account for this and provide comparable figures.
| Injury in CRASH | Detailed severity | Severity classification |
|---|---|---|
| Deceased | Killed | Killed |
| Broken neck or back | Very Serious | Serious |
| Severe head injury, unconscious | Very Serious | Serious |
| Severe chest injury, any difficulty breathing | Very Serious | Serious |
| Internal injuries | Very Serious | Serious |
| Multiple severe injuries, unconscious | Very Serious | Serious |
| Loss of arm or leg (or part) | Moderately Serious | Serious |
| Fractured pelvis or upper leg | Moderately Serious | Serious |
| Other chest injury (not bruising) | Moderately Serious | Serious |
| Deep penetrating wound | Moderately Serious | Serious |
| Multiple severe injuries, conscious | Moderately Serious | Serious |
| Fractured lower leg / ankle / foot | Less Serious | Serious |
| Fractured arm / collarbone / hand | Less Serious | Serious |
| Deep cuts / lacerations | Less Serious | Serious |
| Other head injury | Less Serious | Serious |
| Whiplash or neck pain | Slight | Slight |
| Shallow cuts / lacerations / abrasions | Slight | Slight |
| Sprains and strains | Slight | Slight |
| Bruising | Slight | Slight |
| Shock | Slight | Slight |
Before the introduction of CRASH, the police used the following classifications for determining collision severity:
- a fatal injury is one which causes death less than 30 days after the collision;
- a fatal collision is an collision 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 collision, and which is in one (or more) of the following categories:
- an injury for which a person is detained in hospital as an in-patient, or
- 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
- any injury causing death 30 or more days after the collision;
- a serious collision 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 collision 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 collisions.
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 a slight injury in collisions that previously would have taken place at higher speeds and so might previously have resulted in a 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 collisions 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 collisions 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.
Comparisons with other sources of injury road collisions data
Injury road collisions, and their associated casualties, are only recorded in Stats 19 (the data collection which is the source for the figures presented throughout the main body of this publication) if they occur on public roads and become known to the police within 30 days. This means that the number of collisions and casualties collected through Stats 19 is likely to be lower than the true number.
This section provides high level comparisons between the data collected through the Stats 19 statistical returns made by Police Scotland and alternative sources as a means of assessing the coherence and completeness of the Stats 19-derived statistics.
This sections also compares trends for different casualty severities within the Stats 19 data collection.
National Records for Scotland deaths data
National Records for Scotland (NRS) produce annual figures for deaths due to road traffic accidents. As these are derived from information recorded on death certificates, they provide an alternative source of information for the road fatalities presented elsewhere within this publication.
Figure 15 shows that overall, the number of road traffic accident deaths published by NRS are similar to the fatalities reported within road casualties publications, with both sources generally rising and falling together
Where there are differences, figures from NRS are generally higher. This is to be expected as there are some definitional differences between the two sets of figures. In particular, for a fatality to be included within the Stats 19 data, the fatality must occur within 30 days of the traffic collision, whereas there is no such cut-off for NRS figures.
Further information on data collected for causes of death can be found on the NRS website.
Emergency admissions resulting from road traffic accidents
Public Health Scotland (PHS) routinely publish figures for emergency hospital admissions resulting from road traffic accidents within their Unintentional Injuries publication. Although there are differences between emergency hospital admissions and the serious casualties collected through Stats 19 (serious casualties may not involve an admission to hospital), these still offer a source for broad comparisons.
The Unintentional Injuries publication by PHS presents data for financial years, therefore the Stats 19 figures presented here have also been calculated using financial years and will differ from figures elsewhere in this publication.
Figure 16 shows that unadjusted Stats 19 figures and emergency hospital admissions followed a broadly similar trend over the past two decades, until the break in the time series caused by the introduction of CRASH in 2019/20 (see Introduction). Both sources showed a decline to all-time lows in 2017/18.
Over the past two decades, emergency admissions have consistently been higher than the unadjusted serious casualties collected through Stats 19. Emergency admissions were between 32% and 48% higher than serious casualties between the years 2004/05 and 2018/19 and this gap widened in the years immediately prior to the introduction of CRASH.
Using adjusted figures for serious casualties brings historic Stats 19 casualties more into line with emergency admissions, but highlights a greater drop in Stats 19 casualties over time compared with emergency admissions.
There are potential reasons for differences in trends between emergency admissions and Stats 19 data, some of which may have been further affected by the introduction of CRASH in mid-2019. These include:
- Reduced reporting of road accidents by the public to the police;
- Changes in the way in which Police Forces report collisions in their Stats 19 returns;
- An increase in the proportion of road casualties going to hospital;
- Changes in hospitals' practices (which might result in an increased proportion of the casualties who go to A&E departments being admitted to hospital, or a larger proportion of admissions as a result of a road accident being identified as such in hospitals' data);
- Road safety improvements which disproportionately reduced injuries classified as serious in Stats 19 but which do not involve being admitted to hospital.
The Transport Scotland statistics team will be taking forward work over the summer period to explore in more detail the differences between emergency admissions and Stats 19 data.
Further information on the Unintentional Injuries publication can be found on the Public Health Scotland website.
Scottish Household Survey
The Scottish Household Survey (SHS) is a representative, annual survey of private households in Scotland and collects information on a range of topics, including transport. The SHS previously included questions which asked respondents whether they had been involved in a road collision, and if so whether they had been injured. The survey also asked respondents whether the police came to know about the collision. The questions were asked in their most recent form in 2012,2014,2016,2019, and 2021.
The latest available data from 2021 shows that 0.8% of respondents reported that they had been injured in a road collision in the two years prior. The figure for 2021 is not directly comparable with earlier years due to pandemic-related changes to the survey in that period, but given the uncertainty around survey estimates it is also difficult to draw any firm conclusions regarding trends over time in earlier years [Table 5].
| Year | Percentage injured | Confidence interval +/- |
|---|---|---|
| 2012 | 1.7 | 0.5 |
| 2014 | 0.7 | 0.3 |
| 2016 | 1.0 | 0.4 |
| 2019 | 1.2 | 0.4 |
| 2021 | 0.8 | 0.4 |
Given the small number of respondents that reported being injured in a collision in a given year (for illustration there were 22 in 2021, and 36 in 2019), there is very large uncertainty around single-year estimates for the proportion of the injury collisions that were reported to the police. This means that it is not possible to assess trends in collision-reporting using the SHS. However, a combined figure for 2012-2021 suggests that around a third of injury collisions (34%) were not reported to the police over this period. The confidence interval around this estimate is +/- 9 percentage points.
These estimates may be subject to survey recall issues as well as differences between what respondents would perceive as an injury road collision and the stricter definitions used in Stats 19 (for example, injuries sustained on private ground but may be included by a respondent in the Scottish Household Survey, but are not included in Stats 19). However, they do underline that a significant proportion of injury collisions are not reported to the police and provide one estimate for the scale of this under-reporting.
Further information on the Scottish Household Survey including survey questionnaires can be found on the Scottish Government website.
Differences between severities
Figure 17 presents trends for the different severities of casualties collected within the Stats 19 data collection (fatal, adjusted serious, and slight). This analysis uses a rolling 3 year average to smooth out single year fluctuations, particularly in fatalities, and is indexed to the 2004-2006 average in order to straightforwardly compare changes over time between different severities.
All three severities show a clear fall over time, although fatalities fell more quickly than serious and slight casualties between 2009 and 2015. In recent years differences have emerged, with serious casualties falling more than fatalities, and slight casualties falling more than serious casualties.
There are potential reasons the differing trends between severities, some of which could have been further affected by the introduction of CRASH. These include:
- Reduced reporting of less serious road accidents by the public to the police (and hence reduced reporting in Stats 19);
- Changes in the way in which Police Scotland reports collisions of differing severity in their Stats 19 returns;
- Road safety improvements which disproportionately reduced the number of less serious injuries.
The Transport Scotland statistics team will be taking forward work over the summer period to explore differences in trends between severities, including the impact of CRASH and severity adjustments.
Access to data
Almost all of the data collected for this statistical bulletin are available as part of a GB-wide dataset on data.gov.uk
Further detail be made available on request, subject to consideration of legal and ethical factors. Please contact Transtat@transport.gov.scot for further information.