What factors contribute to a crash?

Crashes are coded by police using a set of parameters that cover almost every eventuality. There are also contributing factors which are recorded in order of importance.

Road environment contributed

Slippery road due to weather – roads can be especially slippery when there’s light rain after a long dry spell. Areas of tar bleed, where the aggregate in the road has worn away and just left black tar, are very slippery when the weather is extremely hot (due to melting), wet or cold.

Deposit on road (e.g. oil, mud, chippings) – motorists should be careful on newly sealed road surfaces because of loose chippings, and also around farm gates

Poor or defective road surface (e.g. pot holes and degradation)

Sunken, raised or slippery inspection cover (especially dangerous for motorbikes)

Road layout (e.g. bend, hill, narrow carriageway)

Temporary road layout (e.g. contraflow)

Animal or object in carriageway

Inadequate or masked signs or road markings

Defective traffic signals

Traffic calming (e.g. speed cushions, road humps, chicanes)

Vehicle defects

Tyres illegal, defective or under-inflated – tyres with less than 3mm tread have an exponential drop-off in their effectiveness in wet conditions

Defective lights or indicators

Defective brakes

Defective steering or suspension

Defective or missing mirrors – watch also for mirrors that aren’t set up correctly

Overloaded or poorly loaded vehicle or trailer – an unbalanced trailer can become very unstable at speed.

Injudicious action

Following too close (i.e. tailgating)

Exceeding the speed limit

Disobeyed give way or stop sign or markings

Disobeyed automatic traffic signal

Travelling too fast for conditions

Cyclist entering road from pavement

Illegal turn or direction of travel

Disobeyed pedestrian crossing facility

Vehicle travelling along pavement

Disobeyed double white lines

Driver/rider error or reaction

Failed to look properly

Failed to judge other person’s path or speed – this is common when a driver has drunk alcohol

Poor turn or manoeuvre

Sudden braking

Swerved

Junction overshoot

Junction restart (moving off at junction)

Failed to signal or misleading signal

Too close to cyclist, horse or pedestrian

Loss of control

Impairment or distraction

Impaired by alcohol

Impaired by drugs (illicit or medicinal)

Driver using mobile phone

Fatigue

Distraction in vehicle

Distraction outside vehicle

Illness or disability, mental or physical

Uncorrected, defective eyesight

Rider wearing dark clothing

Not displaying lights at night or in poor visibility

Behaviour or inexperience

Careless, reckless or in a hurry

Learner or inexperienced driver/rider

Aggressive driving

Nervous, uncertain or panic

Unfamiliar with model of vehicle – anything from turning on the wipers instead of the indicators and therefore giving a misleading signal, to misjudging the size of the vehicle.

Inexperience of driving on the left

Driving too slow for conditions or slow vehicle (e.g. tractor)

Vision affected by

Stationary or parked vehicle(s)

Road layout (e.g. bend, winding road, hill crest)

Dazzling sun

Rain, sleet, snow or fog

Spray from other vehicles

Dazzling headlights

Vehicle blind spot

Vegetation

Buildings, road signs, street furniture

Visor or windscreen dirty, scratched or frosted, etc

Pedestrian only (casualty or uninjured)

Failed to look properly

Careless, reckless or in a hurry

Failed to judge vehicle’s path or speed

Crossing road masked by stationary or parked vehicle

Impaired by alcohol (drink walking)

Impaired by drugs (illicit or medicinal)

Dangerous action in carriageway (e.g. playing)

Wrong use of pedestrian crossing facility

Pedestrian wearing dark clothing at night

Disability or illness, mental or physical

Special codes

Stolen vehicle

Vehicle in course of crime

Emergency vehicle on a call

Vehicle door opened or closed negligently.