What sources of data are used to count and describe serious injuries on Irish roads?
The RSA has historically used collision records from the Irish Road Traffic Collision database, transferred from An Garda Síochána, to report on serious injuries from road traffic collisions.
More recently, the RSA has also started to study serious injuries in hospital data using Ireland’s national database of hospital discharges. This hospital database is called HIPE (Hospital In-Patient Enquiry) and is managed by the HSE.
To study hospital data, the RSA is working in collaboration with the HSE National Health Intelligence Unit, and the School of Medicine in Trinity College Dublin (TCD).
Why is the RSA studying hospital data to count and describe serious injuries?
International research evidence indicates that counting serious injuries from road crashes is challenging, and that using police data as the unique data source will understate their true number. Some common reasons for this may be:
- The police may not be alerted to a collision, especially when the collision does not involve a motor vehicle. For instance, when a cyclist hits a kerb and is injured they may call the ambulance but may not report this incident to the police.
- Police members who attend the scene of the crash do not have medical training. Therefore, they may not be able to detect injuries, especially in cases where they are not very evident. In addition, the severity of an injury may only become apparent in the aftermath of the crash.
To overcome these limitations, the European Commission has requested Member States to study serious injuries in hospital data in addition to using police data, and to use a new definition of a serious injury based on information available in medical reports. The use of hospital data and the common medical definition of a serious injury by Member States will also allow the Commission to perform comparisons between countries and monitor serious injury trends in the region.
What are the definitions of serious injury used in Garda and hospital data?
In Garda data, a serious injury is one for which the person is detained in hospital as an in-patient, or any of the following injuries whether or not detained in hospital: fractures, concussions, internal injuries, crushing, severe cuts and lacerations, or severe general shock requiring medical treatment.
In hospital data, we use the medical definition of a serious injury requested by the European Commission. We determine the severity of injuries using an injury severity scoring scale, the Abbreviated Injury Scale (AIS). When a casualty is assigned a maximum score of 3 or more in the AIS scale, they are considered as seriously injured from a clinical point of view, and are called MAIS3+ casualties.
MAIS3+ casualties are those with a higher probability of having long-term consequences from the injuries in their life after the collision.
Why is the RSA reporting on all hospitalised casualties?
When working with hospital data, we count the total number of casualties who were admitted to hospital as in-patients, on an emergency basis, and who sustained at least one injury from a road traffic collision.
As explained in Q3, we use the AIS scale to estimate the number of casualties with the most serious injuries (MAIS3+). The AIS scale also allows us to determine the number of casualties who sustained injuries of minor-to-moderate severity. These minor-to-moderate injuries, although not the most serious ones, can also have some level of impact on the casualties every-day life, and are also relevant for road safety and public health. We add the number of casualties having injuries of all severities (minor-to-moderate and serious) to obtain the total number of hospitalised casualties.
All hospitalised casualties are in-patients, and as such, they should be counted as seriously injured casualties when applying the definition of a serious injury used in Garda data (see Q3). Hence, counting the number of all hospitalised casualties allows us to have an approximate estimate of the size of the difference in the number of casualties recorded in hospital and Garda records.
What information can we obtain from Garda data?
Collision records include information on the crash, such as the exact location and the date/time of the day in which occurred, road type and characteristics, and vehicles involved. Information on the casualty is also described, including the type of road user, their age and gender, and contributory actions. The only information available on injuries is a broad categorisation of these being fatal, serious or minor.
What information can we obtain from hospital data?
Hospital records describe information on the casualty, including the type of road user and their age and gender; the date of hospital admission; a detailed assessment of the injuries sustained and their severity; and information on clinical outcomes such as the number of days spent at hospital as in-patient, the number of days a casualty received critical care, and the destination at discharge. Limited information on the crash is available, for example the other vehicle involved in the crash, and if the crash occurred on a public road. No information on the location of the crash is available.
Why is it important for Ireland to use hospital data to study serious injuries?
Both Garda and hospital data provide very valuable and unique information on serious injuries. Using hospital data to complement Garda data on serious injuries allows us to have a better estimate of the number of serious injuries on Irish roads, which is key for monitoring progress towards Vision Zero and for informing the development of evidence-based interventions.
Hospital data provides a more holistic understanding of the serious injury problem. Information on the casualty such as the accurate injury profile, and the description of clinical outcomes, is helpful to understand the human and health impact for road users after a crash. This is valuable new information that the RSA did not have before getting access to clinical information.
The collaboration between the RSA, the HSE, and TCD will help to incorporate the public health perspective to road safety, which is an important step towards understanding the injury burden of road traffic collisions, and integrating the road safety message in health promotion initiatives.
In particular, hospital records allow a better estimate of the scale of serious injuries among cyclists, and of single-cyclist collisions, which are less frequently recorded in Garda records. This will inform the design of new evidence-based interventions focused on this population.
Studying hospital information allows Ireland to comply with the European Commission mandate of using the medical definition of serious injury and contribute to the understanding and monitoring of the serious injury issue within the region.
Why is the number of serious injuries in hospital data much larger than in Garda data?
From the study of records for the period 2014-2022, we determined that, in general, the number of hospitalised casualties with injuries from road traffic collisions is higher than the number of serious injuries recorded by An Garda Síochána. The size of this difference can vary for each road user type. For instance, the number of cyclists recorded in hospital data is between 2 and 3 times higher than the number of cyclists with serious injuries in Garda records. For pedestrians, this difference between data sources is much smaller.
As mentioned in Q2, this difference between data sources has been also observed in other countries, and might be explained by the police not being alerted of a crash; or by injuries not being detected or being misclassified as non-serious due to the assessment of the injuries sustained being done by a police member and not by a medic.
Why is the difference in the total number of serious injuries so large for cyclists?
In addition to the reasons explained in Q8, there might be additional factors contributing to explain the difference between the data sources that are linked to each road user in particular. Our data for the period 2014-2022 shows that an important difference between Garda and hospital cyclist records is related to the collision type in which they received their injuries. In hospital records, 64% of all hospitalised cyclists were injured in a single cyclist collision. In Garda records, this collision type represented only 17% of cyclist serios injuries.
A single-cyclist collision is a crash including one moving vehicle (the bicycle). Our research indicates that the most common circumstances for single-cyclist collisions include an interaction of the bicycle with the road surface, loss of control of the bicycle, a collision with a kerb/footpath, or avoidance of another vehicle.
Where can I find more information on the methodology to count serious injuries in hospital data?
You can find a summary of the methodology to estimate serious injuries in hospital data here.
Is the hospital data processed by the RSA anonymous?
All the hospital information we analyse is anonymous, which means that it does not include the name, address, or any other direct identifier of a casualty. In our reports including hospital data, we also avoid the disclosure of small numbers of casualties (<5), to avoid the possibility of a casualty being indirectly identified by a combination of their characteristics (such as age, road user mode, and number of days spent at hospital).
What reports are publicly available from the RSA on serious injuries using hospital data?

We are currently working on a report series focused on serious injuries for each road user type, using hospital and Garda data from 2014 onwards. Published reports from this series can be found at this link, including a high-level report on the total and trend on serious injuries over 2014-2022, a cyclist report (2014-2022), an infographic on cyclists serious injuries, and a methodology report. Future reports will be focused on pedestrians, motorcyclists, car users, and groups of casualties by age (children, young, and senior).

The European Road Safety Observatory (ERSO) published a Facts & Figures report on serious injuries in 2023, which features serious injury trends in the region and includes data from Ireland.

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