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From Scores to Patients: Rethinking ‘Injury’

Explaining the language of injury scoring

When researchers, clinicians, and policymakers talk about “road injury”, they often turn to a shared set of tools: the Abbreviated Injury Scale (AIS) and the scores built upon it. These scores provide a common language for comparing injuries and outcomes across systems, countries, and decades.

AIS assigns each injury a severity score from 1 (minor) to 6 (maximal, unsurvivable). It is anatomy-based, not prognosis-based. The scale is developed and maintained by the Association for the Advancement of Automotive Medicine (AAAM). Access to the dictionaries and related tools requires purchase or licence agreements, which can limit universal accessibility.

The highest single AIS score sustained by a patient. For example, if someone has injuries scored AIS-2, AIS-3 and AIS-4, their MAIS is 4.

The Injury Severity Score (ISS) adds together the square of the three worst injuries in different parts of the body. It was created in the 1970s and is commonly used to identify major trauma—usually when the score is 15 or higher.

Introduced in the 1990s, NISS works like ISS but drops the “different regions” rule. It simply takes the three highest AIS scores—regardless of body region—squares them, and sums them. This often gives a more accurate reflection of risk when multiple serious injuries occur in the same region.

These measures have become indispensable. They underpin trauma registries, performance benchmarking, and even international road-safety targets—for example, the European Union tracks “MAIS-3+” injuries as its measure of serious road traffic injury.

How meaningful are these scores?

Within a single AIS level lies a striking diversity of patient experiences. Consider AIS-3 (“serious”) injuries:

  • Some AIS-3 injuries are life-changing. Complex limb injuries, for instance, may result in chronic pain, multiple operations, or permanent limitations in mobility and function.
  • Others, also coded AIS-3, may be managed effectively with modern techniques, allowing patients to return to normal function within weeks.

Both are classified identically, yet the consequences for the individual and for health, social care, and the economy are worlds apart.

What the system misses

AIS and its derivatives were designed to reflect anatomical threat to life. That focus brings clarity, but also leaves important gaps:

  • Psychological injury. PTSD, depression, and anxiety can follow collisions and entrapments, yet AIS captures none of these.
  • Return to work and function. Health-related quality of life, employment, and role participation are all central to recovery, but fall outside the AIS/ISS framework.
  • Foetal outcomes. Trauma in pregnancy may result in fetal loss even when maternal injuries score low on AIS. This profound harm is not counted.

When health systems are judged by metrics that omit these outcomes, the true burden of road injury; particularly for women, pregnant people, and those with limited access to rehabilitation will be underestimated.

Barriers to equitable participation

Because AIS is licensed and fee-based, access may be restricted for smaller services, researchers in low- and middle-income countries, or patient advocates. This creates another form of inequity: those most affected by road injury may not have equal opportunity to engage with the very metrics that define policy and resource allocation.

So, are we measuring road injury fairly?

AIS, ISS, and NISS are essential for international comparability. They provide a consistent foundation for research and policy. But if we want truly patient-centred, equitable post-collision care, these scores are necessary but not sufficient.

Fair measurement would mean:

  • Recognising and reporting psychological sequelae.
  • Tracking functional recovery, including return to work.
  • Incorporating process measures that matter, such as time to release from entrapment or time to haemorrhage control.
  • Adding maternal–fetal outcomes when trauma involves pregnancy.

If our goal is safer roads and better care, we must measure what matters most to people-not just what’s easiest to code. AIS, ISS, and NISS should be the starting point of the conversation, not the end.  At IMPACT, we want to explore new, pragmatic ways of measuring road injury that are fair, patient-centred, and globally applicable. We invite you to collaborate with us. What outcomes should be added alongside AIS/ISS? How can they be collected reliably across different contexts? How can we ensure equity in the way road injury is measured and reported? Share your ideas. Let’s rethink road injury together.
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