Annex A: Background, sources and definitions

Key Reported Road Casualties Scotland 2020

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 accidents in which a vehicle is involved that occur on roads (including footways) and that result in personal injury. Only injury accidents reported to the police are included. 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, in which no people are injured, are not included in these statistics.

There could be many non-fatal injury accidents 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 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. From the middle of 2019, Police Scotland have used the CRASH system for recording severity details of accidents. Table 2 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.

Table 3: Classification of injury severity using the CRASH reporting system
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 accident severity:

  • 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:
  • 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 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 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 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.

Provisional data

Data used in this publication were extracted from Transport Scotland’s reported road accident statistical database in May 2021. 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 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 3: Difference between the provisional and final number of recorded casualties, broken down by severity, 2001 – 2019.
Number of casualties Rate (%)
Year Killed Seriously injured Slightly injured All severities Killed Seriously injured Slightly injured All severities
2001 0 1 4 5 0.0% 0.0% 0.0%
2002 1 9 0 10 0.3% 0.3% 0.1%
2003 -1 9 29 37 -0.3% 0.3% 0.2% 0.2%
2004 -1 30 130 159 -0.3% 1.1% 0.8% 0.9%
2005 0 58 -29 29 2.2% -0.2% 0.2%
2006 0 31 159 190 1.2% 1.1% 1.1%
2007 -1 66 85 150 -0.4% 2.8% 0.6% 0.9%
2008 -2 33 -18 13 -0.7% 1.3% -0.1% 0.1%
2009 0 0 17 17 0.1% 0.1%
2010 0 4 6 10 0.2% 0.1% 0.1%
2011 0 2 5 7 0.1% 0.0% 0.1%
2012 4 15 82 101 2.3% 0.8% 0.8% 0.8%
2013 0 5 0 5 0.3% 0.0%
2014 -3 5 23 28 -1.5% 0.3% 0.2% 0.2%
2015 0 -1 13 18 -0.1% 0.1% 0.2%
2016 0 4 16 20 0.2% 0.2% 0.2%
2017 0 9 28 37 0.6% 0.4% 0.4%
2018 1 1 7 9 0.6% 0.1% 0.1% 0.1%
2019 -3 15 32 44 -1.8% 0.7% 0.6% 0.6%

On evaluating progress against targets Reported Road Casualties

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 2004-08 and falls, by a constant percentage reduction in each subsequent year, to the target for 2020. 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 Figures 12, 13 and 14 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% 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% and 4.61%. For child killed 4.67% and 4.37% or seriously injured 7.41% and 6.90%.