Annex A: Background, sources and definitions
Sources of the data
The figures in this bulletin were compiled from Stats19 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. More information about this undercounting is provided in Reported Road Casualties Scotland 2010, in the section entitled 'Estimating under-counting of Road Casualties in Scotland'.
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 3 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.
| 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.
Provisional data
Data used in this publication were extracted from Transport Scotland’s reported road collision statistical database in April 2023. 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 4 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%.
Table 4: Difference between the provisional and final number of recorded casualties, broken down by severity, 2001 – 2021
| Year | Killed | Seriously injured | Slightly injured | All severities |
|---|---|---|---|---|
| 2001 | 0 | 1 | 4 | 5 |
| 2002 | 1 | 9 | 0 | 10 |
| 2003 | -1 | 9 | 29 | 37 |
| 2004 | -1 | 30 | 130 | 159 |
| 2005 | 0 | 58 | -29 | 29 |
| 2006 | 0 | 31 | 159 | 190 |
| 2007 | -1 | 66 | 85 | 150 |
| 2008 | -2 | 33 | -18 | 13 |
| 2009 | 0 | 0 | 17 | 17 |
| 2010 | 0 | 4 | 6 | 10 |
| 2011 | 0 | 2 | 5 | 7 |
| 2012 | 4 | 15 | 82 | 101 |
| 2013 | 0 | 5 | 0 | 5 |
| 2014 | -3 | 5 | 23 | 28 |
| 2015 | 0 | -1 | 13 | 18 |
| 2016 | 0 | 4 | 16 | 20 |
| 2017 | 0 | 9 | 28 | 37 |
| 2018 | 1 | 1 | 7 | 9 |
| 2019 | -3 | 15 | 32 | 44 |
| 2020 | -1 | 8 | 41 | 48 |
| 2021 | 1 | 19 | 60 | 80 |
| Year | Killed | Seriously injured | Slightly injured | All severities |
|---|---|---|---|---|
| 2001 | n/a | 0.00% | 0.00% | 0.00% |
| 2002 | 0.30% | 0.30% | n/a | 0.10% |
| 2003 | -0.30% | 0.30% | 0.20% | 0.20% |
| 2004 | -0.30% | 1.10% | 0.80% | 0.90% |
| 2005 | n/a | 2.20% | -0.20% | 0.20% |
| 2006 | n/a | 1.20% | 1.10% | 1.10% |
| 2007 | -0.40% | 2.80% | 0.60% | 0.90% |
| 2008 | -0.70% | 1.30% | -0.10% | 0.10% |
| 2009 | n/a | n/a | 0.10% | 0.10% |
| 2010 | n/a | 0.20% | 0.10% | 0.10% |
| 2011 | n/a | 0.10% | 0.00% | 0.10% |
| 2012 | 2.30% | 0.80% | 0.80% | 0.80% |
| 2013 | n/a | 0.30% | n/a | 0.00% |
| 2014 | -1.50% | 0.30% | 0.20% | 0.20% |
| 2015 | n/a | -0.10% | 0.10% | 0.20% |
| 2016 | n/a | 0.20% | 0.20% | 0.20% |
| 2017 | n/a | 0.60% | 0.40% | 0.40% |
| 2018 | 0.60% | 0.10% | 0.10% | 0.10% |
| 2019 | -1.80% | 0.70% | 0.60% | 0.60% |
| 2020 | -0.70% | 0.50% | 1.20% | 1.00% |
| 2021 | 0.70% | 1.20% | 1.80% | 1.60% |