Appendix C - Definitions and points to note
The definition of severity used in the Road Collision statistics
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.
For the purposes of the Road Collisions statistical returns:
- 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 (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 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.
From the middle of 2019 Police Scotland started to use the new CRASH system for recording details of an collision. This provides a more detailed definition of the severity of casualties. The following table lists the options for determining how severe an injury is. It should be noted that in some cases in 2020 although the most severe injury appears to be slight, if the casualty was subsequently admitted to hospital the casualty severity was classed as serious. The introduction of CRASH has meant that the severity of injuries is recorded more accurately and has led to an increase in the number of serious injuries. Figures are therefore not directly comparable with those for the previous years.
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 or ankle or foot | Less Serious | Serious |
| Fractured arm or collarbone or hand | Less Serious | Serious |
| Deep cuts or lacerations | Less Serious | Serious |
| Other head injury | Less Serious | Serious |
| Whiplash or neck pain | Slight | Slight |
| Shallow cuts or lacerations or abrasions | Slight | Slight |
| Sprains and strains | Slight | Slight |
| Bruising | Slight | Slight |
| Shock | Slight | Slight |
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 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 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 collisions which is 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% 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 collision and by a clerk who bases the code on a police officer’s written description of the collision.
Other definitions
Collision
The statistical returns include only those collisions which result in personal injury, which occur on roads (including footways), in which a vehicle is concerned, and which become known to the police. The vehicle need not be moving and it need not be in collision. The statistics are therefore of injury road collisions only: damage-only collisions are not included in the figures.
Adults
People aged 16 and over.
Built-up roads
collisions 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 collision 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 collision 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.
Buses and coaches
Include works’ buses and (in past years) trams and trolley buses. Vehicles are coded according to their construction, irrespective of their use at the time of the collision. Thus, vehicles of bus construction which are privately licensed are included under ‘buses and coaches’, while Public Service Vehicle licensed minibuses are included under minibuses.
Cars
Include estate cars and three-wheeled cars.
Casualty
A person killed or injured in an collision. One collision may give rise to several casualties.
Children
People under 16 years old.
Darkness
From half an hour after sunset to half an hour before sunrise, ie ‘lighting-up time’.
Drivers
Persons in control of vehicles other than pedal cycles and two-wheeled motor vehicles.
Goods vehicles
Vans, lorries, tankers, milk floats, tractor units travelling without their trailer units.
Heavy goods vehicles
From 1994, heavy goods vehicles have been defined as goods vehicles with a maximum permissible gross vehicle weight of more than 3.5 tonnes. Prior to 1994, they were defined as those with an unladen weight of more than 1.5 tons (1.52 tonnes).
Junction
A place at which two or more roads meet, whatever the angle of the axes of the roads (including roundabouts), or within 20 metres of such a place.
Killed
Sustained injuries which caused death less than 30 days after the collision.
Light goods vehicles
From 1994, light goods vehicles have been defined as goods vehicles with a maximum permissible gross vehicle weight of up to 3.5 tonnes. Prior to 1994, they were defined as those with an unladen weight of 1.5 tons (1.52 tonnes) or less.
Major roads
Motorways and A roads.
Minor roads
B roads, C roads and unclassified roads.
Motorcycles
Includes all two wheeled motor vehicles.
Motorists
The drivers or riders of motor vehicles (including, for example, motorcyclists).
Motorways
Include A(M) roads.
Non built-up roads
Roads for which the normal speed limit (ignoring any temporary speed limits) is more than 40mph.
Other vehicles
Include ambulances, fire engines, pedestrian-controlled vehicles with motors, railway trains or engines, refuse vehicles, road rollers, tractors, excavators, mobile cranes, tower wagons, army tanks, etc – and from 1999, motor caravans. Other non-motor vehicles include those drawn by an animal, ridden horses, invalid carriages without motor, street barrows, etc.
Passengers
Occupants of vehicles, other than the person in control, including pillion passengers.
Pedal cycles
Including toy cycles ridden on the carriageway, tandems and tricycles. Pedal cyclists includes any passengers of pedal cycles.
Pedestrians
Includes people riding toy cycles on the footway, people pushing bicycles, people pushing or pulling other vehicles or operating pedestrian-controlled vehicles, those leading or herding animals, occupants of prams or wheelchairs, and people who alight safely from vehicles and are subsequently injured.
Riders
People in control of pedal cycles or two-wheeled motor vehicles.
Road users
Pedestrians and vehicle riders, drivers and passengers.
Trunk roads
Roads for whose upkeep Scottish Government Ministers are responsible.
Users of a vehicle
All occupants, ie driver (or rider) and passengers, including persons injured while boarding or alighting from the vehicle.
Vehicles involved in collisions
Any vehicle directly involved in an collision where at least one injury is sustained by a pedestrian or vehicle driver, rider or passenger. Vehicles which collide after the initial collision which caused injury are not included, unless they aggravate the degree of injury or lead to further casualties.
Some other points to note
Driver and casualty postcodes, and estimated distances between homes and the locations of collisions
The straight line (or as the crow flies) distance between the location of the collision and the home of a driver, rider or casualty was estimated using the postcode of the person’s home. The grid co-ordinates of the centre of the postcode were obtained from the National Records of Scotland postcode directory file. These were taken as an approximation to the grid co-ordinates of the person’s home, and used in conjunction with the grid co-ordinates of the location of the collision (as reported by the police) to estimate the distance. A similar approach was used in the small proportion of cases where there was only the start of a postcode (eg the police might record EH10 if they knew that someone lived in Edinburgh 10, but they could not provide the full postcode) or where only the postal district or postcode sector could be matched with the postcode directory. A distance could not be estimated if the postcode were blank, coded not known or non-UK resident, did not contain a valid postal district, or were for a place outwith Scotland.
Estimates of the total volume of road traffic
Some tables include estimates of traffic volumes, or collision or casualty rates calculated from them. The traffic estimates were provided by the Department for Transport (DfT), which produces estimates of the total volume of road traffic for Scotland and for other parts of Great Britain.
DfT’s estimates are based on an urban/rural classification of roads, not on the built-up/non built-up classification of roads used in the traffic estimates that were made up to 2002 (which is still used for the collision and casualty statistics). In general:
- an urban road is a road (other than a Motorway) that lies within the boundaries of an urban area with a population of 10,000 or more in 2001;
- a built-up road is one that has a speed limit of 40 m.p.h. or less
As traffic on a particular road can be classed as rural whilst collisions occurring on it classed as built-up, it would be incorrect to estimate an area’s collision rate for built-up roads by dividing its number of collisions on built-up roads by its estimated volume of traffic on urban roads. Therefore, estimates of built-up and non built-up collision rates are provided in Table 5 only for Scotland as a whole – and these estimates may not be precise, due to the nature of the classifications.
In addition, DfT note that whilst their traffic estimates at the regional and national level are robust (and are reported as Accredited Official Statistics), estimates for local authorities should be treated with caution. Traffic estimates at this level are not as robust, due to the sample size of the minor road data.