Guidance

Road casualty statistics: definitions, symbols and conventions

Updated 28 November 2024

This document lists some of the main definitions used within the department’s road casualty statistics.  A brief overview of the statistics and their coverage and further more detailed guidance are also available.

Data definitions 

Adult Persons aged 16 years and over (except where otherwise stated).

Agricultural vehicles Mainly comprises agricultural tractors (whether or not towing) but also includes mobile excavators and front dumpers.

A(M) roads Motorway standard roads that are not titled as ‘motorways’, for example the A1(M). 

Built-up roads Roads with speed limits of 40 mph or less (ignoring temporary limits).  

Buses and coaches Buses or coaches equipped to carry 17 or more passengers, regardless of use. 

Cars Includes taxis, estate cars, 3 and 4 wheel cars, and minibuses, except where otherwise stated. Also includes motor caravans prior to 1999. 

Casualty A person killed or injured in an collision. Casualties are sub-divided into killed, seriously injured and slightly injured. 

Children Persons under 16 years of age (except where otherwise stated). 

Darkness From half an hour after sunset to half an hour before sunrise. 

Daylight All times other than darkness. 

Drivers Persons in control of vehicles other than pedal cycles, motorcycles and ridden animals (see riders). Other occupants of vehicles are passengers. 

Failed breath test This includes

• drivers or riders whose test indicated that they had above the legal limit of alcohol in their blood to drive
• drivers who failed to provide a specimen of breath
• drivers who refused to provide a specimen of breath

Fatal collision A collision in which at least one person is killed. 

Goods vehicles These include tankers, tractor units without their semi-trailers, trailers, articulated vehicles and pick-up trucks. Goods vehicles are further divided into two groups according to vehicle weight (see heavy goods vehicles and light goods vehicles). 

Heavy goods vehicles (HGV) Goods vehicles with a maximum permissible gross vehicle weight of over 3.5 tonnes. 

Injury collision A collision involving human injury or death. 

Killed Human casualties who sustained injuries which caused death less than 30 days (before 1954, about two months) after the collision. Confirmed suicides are excluded. 

KSI Killed or seriously injured. 

Light goods vehicles Goods vehicles, mainly vans (including car derived vans), not over 3.5 tonnes maximum permissible gross vehicle weight. 

Motorcycles Two-wheel motor vehicles, including mopeds, motor scooters and motor cycle combinations. 

Motorways Motorway and A(M) roads. 

Mobility scooter A powered wheelchair or scooter with a maximum weight of 150kg before loaded and a maximum speed of 8mph. 

Non-built-up roads Roads with speed limits over 40 mph. Motorway collisions are shown separately and are excluded from the totals for non-built-up roads. 

Other roads All B, C and unclassified roads, unless otherwise noted.

Other vehicles Other vehicles include ambulances, fire engines, trams, refuse vehicles, road rollers, agricultural vehicles, excavators, mobile cranes, mobility scooters and motorised wheelchairs for example, except where otherwise stated. Also included are non-motorised vehicles, including those drawn by an animal, ridden horse, wheelchairs without a motor, street barrows for example, except where otherwise stated. In certain tables “other vehicles” may also include buses and coaches and/or goods vehicles, as indicated in a footnote. 

Passengers Occupants of vehicles, other than the person in control (the driver or rider). Includes pillion passengers. 

Pedal cycles Includes tandems, tricycles and toy cycles ridden on the carriageway. From 1983, the definition includes a small number of cycles and tricycles with battery assistance with a maximum speed of 15 mph. 

Pedal cyclists Riders of pedal cycles, including any passengers. 

Pedestrians Includes

• children riding toy cycles on the footway
• persons pushing bicycles
• persons pushing or pulling other vehicles or operating pedestrian-controlled vehicles
• persons leading or herding animals
• children in prams or buggies
• people who alight safely from vehicles and are subsequently injured

Riders Persons in control of pedal cycles, motorcycles or ridden animals. Other occupants of these vehicles are passengers. 

Road users Pedestrians and vehicle riders, drivers and passengers. 

Rural roads Major roads and minor roads outside urban areas and having a population of less than 10,000. 

Serious collision One in which at least one person is seriously injured but no person (other than a confirmed suicide) is killed. 

Serious injury The definition of injury severity has changed in recent years and in most police forces is now based solely on the injury recorded from a list of 20 defined injuries.   The classifications of these injuries into different severities is available in the severity adjustment guidance.           

Historically, or in forces not using an injured-based reporting system, a serious injury is defined as an injury for which a person is detained in hospital as an “in-patient”, or any of the following injuries whether or not they are detained in hospital: fractures, concussion, internal injuries, crushings, burns (excluding friction burns), severe cuts, severe general shock requiring medical treatment and injuries causing death 30 or more days after the collision.

The change in the recording of injury severity has impacted on the published statistics, and adjusted figures are used to allow for this.  Further details are available in the severity adjustments guidance.

The information used by the police to determine whether an injured casualty is seriously or slightly injured is typically that which is available within a short time of the collision. This generally will not reflect the results of an in-depth medical examination.

Severity Severity can refer to collision severity or casualty severity. Severity of a casualty refers to whether the casualty was killed, seriously injured or slightly injured. Severity of a collision refers to the severity of the most severely injured casualty (either fatal, serious or slight).

Slight collision One in which at least one person is slightly injured but no person is killed or seriously injured.

Slight injury The definition of injury severity has changed in recent years and in most police forces is now based solely on the injury recorded from a list of 20 defined injuries.  The classifications of these injuries into different severities is available in the severity adjustment guidance.      

Historically, or in forces not using an injured-based reporting system, an injury of a minor character such as a sprain (including neck whiplash injury), bruise or cut which are not judged to be severe, or slight shock requiring roadside attention. This definition includes injuries not requiring medical treatment. 

Speed limits Permanent speed limits applicable to the roadway. 

Taxi Any vehicle operating as a hackney carriage, regardless of construction, and bearing the appropriate district council or local authority hackney carriage plates. Also includes private hire cars. 

Users of a vehicle All occupants, such as driver (or rider) and passengers, including persons injured while boarding or alighting from the vehicle. 

Urban roads Urban roads are those within an area of population of 10,000 or more. Tables produced for years prior to 2017 are based on the 2001 Communities and Local Government definition of Urban Settlements. Tables produced from 2017 are based on the 2011 census data that uses a revised 2001 Communities and Local Government classification.  

Vehicles Vehicles (except taxis) are classified according to their structural type and not according to their employment or category of licence at the time of a collision. 

Vehicles involved in collisions Includes

• vehicles whose drivers or passengers are injured
• vehicles which hit and injure a pedestrian or another vehicle whose driver or passengers are injured
• any vehicle that contributes to the collision

Vehicles which collide, after the initial injury-based collision, are not included unless they aggravate the degree of injury or lead to further casualties. Pedal cycles ridden on the footway are included. 

Statistical terms 

Aggregate data Data collected from multiple sources which is then integrated into a summary.   

Confidence limits There is some uncertainty in the data. The confidence limits are the highest and lowest data points that we are confident that the true value falls between.

Intrinsic trend The true trend that we would measure if we had 100% accuracy in our measurement and capture every casualty without error or uncertainty. 

Statistical significance When we compare figures for the latest year with the previous year, we say that a change is ‘statistically significant’ if we are sufficiently confident (in this case 95% confident) that the difference between the 2 figures is the result of a genuine change, rather than being a product of chance. Otherwise, we say the change is ‘not statistically significant’ – this does not necessarily mean that there is not a genuine change, but that we are not able to determine one exists from the data available, at the 95% level of confidence.

Symbols and conventions used 

Rounding of figures In tables where figures have been rounded, there may be a slight discrepancy between the sum of the constituent items and the total as shown. 

Symbols The following symbols have been used throughout these statistics:

• 0 = nil or negligible (less than half the final digit shown)
• Conversion factor: 1 mile = 1.6093 kilometres
• Billion = One thousand million = 1000,000,000 = 10 to the power 9

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Contact details

Road safety statistics

Email roadacc.stats@dft.gov.uk