Being involved in a road traffic accident can be disorientating and distressing, particularly where people are injured or the circumstances are serious. Alongside the immediate focus on safety and medical care, a formal investigation will often begin to establish what happened, why it happened, and who may be responsible.

The road traffic accident investigation procedure in the UK follows a defined process. This can start at the accident scene and continue through evidence gathering, analysis, and formal reporting. Police act as the lead agency, especially where serious injuries or fatalities are involved, and work to understand the events leading up to the collision and support those affected.

In this guide, the road traffic accidents team at JMW explains the key stages of a road traffic accident investigation, from the moments after a crash through to how findings may be used later, in order to help you understand what to expect from the process.

What to Do Immediately After a Road Traffic Accident

After an accident happens, the first priority is safety. You must stop your car as soon as possible and take steps to protect yourself, your passengers, and other road users. The actions taken in the first moments after a collision can affect how the incident is investigated later.

You should take the following steps at the scene:

• Stop your vehicle as soon as it is safe to do so and switch on your hazard lights
• Check for injuries to yourself and any passengers
• Call the emergency services immediately if anyone is seriously injured or at risk
• Provide basic first aid if it is safe and you are able to do so
• Remain calm and avoid admitting responsibility or blaming the other driver or any other party at the scene
• Be aware of other road users and take reasonable steps to reduce further danger

If the vehicles involved are causing an immediate hazard and it is safe to move them, follow any guidance given by the police or emergency services. If not, leave vehicles in position so the accident scene can be assessed properly.

Taking these steps helps protect everyone involved and allows the road traffic accident investigation procedure to begin on a clear and accurate basis.

Managing Safety and Conduct at the Accident Scene

Once the immediate steps have been taken, attention should remain on safety and appropriate conduct at the accident scene. How people behave at this stage can affect both personal wellbeing and the integrity of the investigation that follows.

You should focus on the following:

• Stay as calm and composed as possible
• Follow instructions given by the police or emergency services when they arrive
• Be mindful of passing traffic and other road users at all times
• Avoid disturbing the scene unless there is a clear safety reason to do so

Maintaining a safe environment reduces the risk of further incidents. It also allows evidence to remain intact. The position of vehicles, visible damage, and conditions at the scene can all affect how liability is determined, and the scene must not be altered if it is possible to avoid doing so.

Where police attend, they may begin making early observations straight away. This can involve noting the location of vehicles, road layout, traffic conditions, and any immediate hazards. Preserving the scene supports an accurate assessment of the circumstances surrounding the collision.

Reporting the Accident

After the immediate situation has been stabilised, the accident must be reported through the appropriate channels. This step should be completed as soon as possible, as you have a legal obligation to report an accident to the police within 24 hours.

You should report the accident to your insurer promptly. Most insurers also require notification within 24 hours, even if the damage appears minor or you do not intend to pursue a claim at that stage. Providing accurate details helps avoid complications later.

There are also circumstances where the police must be informed. This applies if anyone has been injured, if details could not be exchanged at the scene, or if there is damage to property or a risk to road safety.

Where police attend, they will usually prepare a basic collision report. This will record details of those involved, the vehicles, and the circumstances of the incident. Police reports form an early part of the road traffic accident investigation procedure and may be referred to during later review.

What is the role of the police?

In the UK, the local police force is the lead agency for investigating road traffic accidents. The role of the police becomes central where a collision has resulted in serious injuries or a fatal accident, but they may also attend other incidents depending on the circumstances.

When police attend the scene, an investigating officer will take control of the initial response. Officers assess the incident, check on the welfare of those involved, manage safety risks, and decide if specialist resources are needed.

The police have a duty to investigate road deaths and life-changing injuries thoroughly. This includes gathering evidence that may indicate if a criminal offence has been committed and deciding if criminal proceedings should follow. At the same time, officers are expected to provide an investigative response that is sensitive and supportive to those affected.

Where a collision has a wider impact, the police may also work with other agencies. This can include medical services, local authorities, or specialist investigators. Their involvement helps build a clear picture of what happened and supports the overall investigation process.

Exchanging Details and Initial Documentation

After a road traffic accident, you must exchange details with anyone involved in the collision. This is a legal requirement and forms an early part of the investigation process.

You should obtain and provide the following information:

• Names and contact details of all drivers involved
• Registration numbers of the vehicles involved
• Insurance details, including the name of the insurer and policy information
• Details of any passengers present at the time of the accident

Alongside exchanging details, it is advisable to document the accident scene while events are still fresh. This information can be useful later and may help investigators understand what happened.

If it is safe to do so, you should:

• Note the date and time the accident happened
• Record weather conditions and road surface details
• Describe visible damage to each vehicle
• Take photographs of the vehicles involved, their positions, and any damage

This early documentation can support police reports and witness accounts. It can also help preserve accurate details before memories later fade.

Gathering Evidence at the Scene

Once the scene is safe, investigators begin collecting evidence. This stage establishes how the collision happened and what factors may have contributed. Evidence gathered at this point can later be used in police reports, criminal proceedings, or to explain events to those affected.

Investigators will usually focus on the following areas:

• Scene documentation: photographs of the accident scene, vehicle positions, road layout, and traffic conditions
• Physical evidence: skid marks, debris, damage patterns, and the final resting position of the vehicles involved
• Witnesses: details of drivers, passengers, and other road users who saw the incident
• Witness statements: accounts taken as soon as possible while events remain clear in people’s minds
• Environmental factors: weather, lighting, visibility, and road surface conditions at the time of the collision

This evidence helps investigators reconstruct the events leading up to the accident. It can also provide useful information if a personal injury claim is pursued, particularly where there are disputes about fault or the circumstances of the collision.

All evidence must be recorded accurately and preserved carefully. This allows it to be analysed later and relied upon as part of the wider investigation process.

Vehicle Examination and Technical Analysis

After the initial evidence has been gathered, investigators may arrange for a detailed vehicle examination. This stage looks closely at the condition of the vehicles involved and helps identify technical factors that may have contributed to the collision.

Crash investigation officers may remove vehicles from the scene for further inspection. A vehicle examiner will then assess each vehicle, focusing on areas that could affect safety or performance.

This process can include:

• Mechanical defects: checking for faults in braking systems, steering, tyres, or other components
• Damage assessment: examining impact points and deformation to help understand how the collision occurred
• Vehicle systems: reviewing airbags, seatbelts, and other safety features to confirm how they operated
• Vehicle data: where available, retrieving information from onboard systems that may record speed or braking

A vehicle examination may identify faults or failures that were outside the driver’s control. In some cases, mechanical defects or system failures can play a role in how an accident happened, even where it initially appears that a particular vehicle caused the collision.

Where a defect is identified, responsibility may rest with a manufacturer or another party involved in the vehicle’s design, production or maintenance. This means that a person may still be entitled to compensation, even if their vehicle was involved in causing the accident, if a fault contributed to the collision.

Understanding whether technical issues played a part is an important aspect of the investigation. These findings can influence how liability is assessed and may be relevant when considering a personal injury claim.

Reconstructing the Collision and Analysing Events

Once evidence has been gathered, investigators begin analysing it to understand how the collision occurred. This stage focuses on piecing together the events leading up to the road traffic accident and testing different explanations for what happened.

Lead investigators review all available information, including scene evidence, vehicle examination findings and witness statements. They may develop hypotheses about how the incident unfolded and assess each scenario against the evidence collected.

This analysis may involve:

• Reviewing vehicle movements and positions before and after impact
• Considering traffic flow and the behaviour of other road users
• Assessing environmental factors such as weather, visibility and road conditions
• Consulting experts in specialist fields where technical or medical input is required

The aim is to establish the circumstances of the collision as accurately as possible. This process supports decisions on fault, safety lessons, and any further action that may be needed, including liability for the purposes of making a claim.

How Is Digital and Medical Evidence Used?

Modern road traffic accident investigations often rely on digital and medical evidence alongside physical findings. This information can provide additional context and help confirm how a collision happened.

Digital evidence may come from several sources. Investigators may review CCTV footage from nearby premises or road cameras. Dashcam recordings and mobile phone data can also be examined, where relevant, to help establish timings, vehicle movements, or driver behaviour.

Medical evidence is used to understand the injuries sustained and how they relate to the collision. This can include hospital records, assessments from medical professionals, and, in fatal accidents, post-mortem findings. In some cases, further medical evidence is obtained to clarify the sequence of events or the severity of injuries.

All digital and medical material must be handled carefully and lawfully. When combined with other evidence, it supports a clearer understanding of what happened and informs the overall investigation.

How Are the Findings Reported and Collated?

Following evidence gathering and analysis, investigators prepare formal reports. These reports record what is known about the collision and provide a clear account of the circumstances and findings.

In most road traffic accidents, the police prepare a basic collision report. This includes details of the drivers, passengers, vehicles involved, and an outline of how the accident happened. Where a collision results in serious injuries or a fatal accident, the investigating officer will prepare a full report. This contains additional information such as witness statements, vehicle examination findings, and relevant medical evidence.

The police must also consider whether a criminal offence may have been committed. In these instances, officers gather and review evidence that may indicate fault or unlawful behaviour, including the role of alcohol or drugs as potential factors. Decisions about next steps are made in line with the Criminal Procedure Rules. The police assess whether there is sufficient evidence to support criminal proceedings and whether prosecution is in the public interest. Where appropriate, files are prepared for review by the Crown Prosecution Service.

Once completed, information from police investigations is recorded for national analysis. Data is submitted through the STATS19 system, which records details of road traffic accidents across the UK. This system has moved towards injury-based reporting, allowing a clearer understanding of how and why people are injured on the road. These statistics can be found on the government website.

Other organisations use this information to improve road safety. Local authorities study accident patterns to inform road design and traffic management changes. The Department for Transport’s RAIDS programme also conducts no-blame studies to analyse the causes of injuries and support wider safety improvements.

What Additional Considerations Occur in Cases of Serious Injury?

Road traffic accidents that result in serious or life-changing injuries can have a lasting impact on those involved, as well as their families. Alongside the investigative work, there is a responsibility to support people affected in a compassionate and clear way.

The police have a duty to keep injured people and their families informed about what is known and what steps are being taken. This includes explaining the investigation process and providing updates where appropriate. Officers are expected to meet defined standards when investigating serious injury collisions, balancing thorough evidence gathering with sensitivity.

Victim statements play an important role at this stage. These documents explain how the crash has affected daily life, relationships, and future plans. They can help investigators, prosecutors, and the courts understand the wider consequences of the incident beyond the physical evidence, and support the process of making a personal injury claim.

Where injuries are severe, investigations may continue for some time. The focus remains on establishing the circumstances that led to the collision and providing clear explanations to those affected, recognising the long-term impact such injuries can have on life and wellbeing.

What Happens in Cases of Fatal Road Accidents?

When a person dies following a road traffic accident, the investigation process becomes more extensive. The police have a duty to establish the circumstances of the death and to ensure the appropriate authorities are informed.

In these cases, the investigating officer will prepare a full collision report. This will include detailed evidence such as witness statements, scene analysis, vehicle examination findings, and medical information. The police must notify the coroner, who has responsibility for establishing the cause of death through an inquest.

Coroners’ courts consider the evidence gathered during the investigation to understand how the death occurred. This process is not about attributing blame, but about establishing the facts. The police are also required to keep the wider justice system informed, including the courts, where criminal proceedings may be considered.

Officers are expected to approach fatal accident investigations with care and sensitivity. Families may wish to visit the scene of a road death, and this should be carefully managed and clearly communicated. The police must also provide explanations to family members about what is known and how the investigation is progressing, recognising the profound impact such incidents have on those affected.

Can the Findings of an Investigation Affect My Personal Injury Claim?

Investigation findings can have a direct impact on a personal injury claim following a road traffic accident. The evidence collected during the investigation helps explain how the accident happened and provides an objective record of the circumstances surrounding the collision.

Police reports often form a central part of this picture. They can include details of the accident scene, the vehicles involved, witness accounts, and any conclusions reached by the investigating officer. Where a full investigation has taken place, this may also include the findings from vehicle examinations, medical evidence, and analysis of the events leading up to the crash.

These findings can be relevant when considering fault. They may clarify how each driver behaved, whether environmental or mechanical factors played a role, and if any breaches of road traffic law were identified. This information can be particularly helpful where accounts differ or where the circumstances are complex.

Investigation material can also demonstrate the nature and extent of injuries. Medical evidence gathered as part of the investigation may support an understanding of how injuries were caused and how they affect daily life. In cases involving serious or life-changing injuries, this context can be especially important.

JMW uses investigation findings to advise people affected by road traffic accidents and to support their claims with clear, reliable evidence. Understanding what the investigation shows allows informed decisions to be made and ensures the focus remains on achieving a fair outcome based on the facts.