Key points

  • In 2023 there were 66 MAIS3+ casualties – this is an increase of 12% over the year and a decrease of 72% from the peak of 235 in 2002.

  • While the numbers of MAIS3+ casualties are lower than PSNI reported seriously injured, the overall trends are similar: both series have shown a historical decrease followed by signs of levelling off, but with increases in more recent years.

  • Males accounted for seven-tenths (69%) of MAIS3+ casualties in Northern Ireland in the five years from 2019-2023. This is greater than the proportions for male casualties reported in overall hospital admissions (67%) and PSNI serious injuries (62%).

  • Over one quarter (26%) of MAIS3+ casualties from 2019-2023 were aged 70 and over. This differs markedly from the age profile of overall hospital admissions for road traffic collisions and PSNI serious injuries, where 14% and 11%, respectively, were in this age band.

  • Overall, 11% of hospital admissions for road traffic collisions in the five years 2019-2023 have injuries classified as MAIS3+; however, the proportions differ slightly by road user type, ranging from 9% of pedal cyclists having MAIS3+ injuries to 13% of pedestrians and 14% of other road users. 11% of car user and motorcyclist hospital admissions have injuries classified as MAIS3+.

  • Comparing the number of hospital admissions to police reported serious injuries we see that a significant proportion (24% over the 25 years 1999-2023) of SI casualties are not known to the police; however, this historic underreporting has changed in recent years. In every year since 2020 the number of PSNI Serious Injures have exceeded hospital admissions. In the most recent five-year period (2019-2023) PSNI Serious Injuries exceeded Hospital admissions by 22%.

Key infographic

Introduction

The Abbreviated Injury Scale (AIS) is a clinical measure used to classify and describe the severity of injuries; it represents the threat to life associated with the injury. A score of 1 indicates a minor injury, while 6 refers to an unsurvivable injury. A casualty that sustains an injury with a score of 3 or higher on the AIS is classified as clinically seriously injured (MAIS 3+).

AIS Code Injury Example
1 Minor Superficial laceration
2 Moderate Fractured sternum
3 Serious Open fracture of humerus
4 Severe Perforated trachea
5 Critical Ruptured liver
6 Unsurvivable Total severance of the aorta
9 Not Known

This is the ninth report in the series and presents the 2023 update. The MAIS 3+ data in this report are produced using casualty admissions to hospitals in Northern Ireland between 1999 and 2023 with a clinically defined serious injury following a road traffic collision. See methodology on page 14 for further detail.

Hospital Admissions Data Issues: 2022 and 2023

There was an issue with the initial extraction of data for 2022 and as a result this publication will provide revised figures for 2022. Also, data for 2023 includes data extracted from encompass (a new electronic patient record system) for the South Eastern Health and Social Care Trust (HSCT) from 9 November 2023. This subset of the data is classed as “Official Statistics in Development” whilst undergoing evaluation. As a result, users should exercise some caution with this data.

What is the need for MAIS3+?

The current reporting of serious injuries is derived from PSNI data. It is based on the judgement of the reporting police officer, following defined guidelines, rather than on medical expertise. The main limitation is the extent to which PSNI data represents the true level of collisions that occur; research carried out suggests that a considerable proportion of non-fatal casualties in Great Britain (and by extension in Northern Ireland) are not known to the police. The PSNI data are directly comparable with Great Britain and the Republic of Ireland but are not generally considered comparable with other international jurisdictions due to significant differences in the grading of severity of injury which can be applied. Reporting serious injury casualties using MAIS 3+ will therefore provide a more accurate, clinical definition of serious injury, while simultaneously correcting for the historic underreporting of police data and international definitional differences. It is the definition of road traffic serious injury currently recommended by the European Union but, it should be stressed again, is at a much higher severity threshold than the existing PSNI definition.

MAIS 3+ in Northern Ireland

Figure 1 shows the number of clinically seriously injured (MAIS 3+) road casualties in Northern Ireland from 1999 to 2023. The series peaked in 2002 with 235 serious injury (SI) casualties, after which numbers began to fall (with a temporary rise in 2006). Looking at the most recent years, there is evidence that the historic downward trend is levelling off; there was a peak of 98 clinical SIs in 2012, followed by a decrease of over one-third (37%) to 62 in 2013. Last year’s revised 2022 figure is the series low with 59 clinical Sis, followed by 66 in 2023.

There has been considerable variability year-on-year across the period, although this is to be expected given the relatively small number of admissions in Northern Ireland that meet the higher MAIS 3+ severity threshold. For this reason, the smoothed trend is also presented (3-year rolling average).

Figure 1: MAIS 3+ road casualties: Northern Ireland, 1999-2023
Annual trend
Rolling average trend
Data
Year MAIS 1-2 MAIS 3+ MAIS Unknown Total
1999 1,891 204 334 2,429
2000 1,794 210 405 2,409
2001 1,819 234 352 2,405
2002 1,723 235 332 2,290
2003 1,406 185 274 1,865
2004 1,365 195 273 1,833
2005 1,278 178 239 1,695
2006 1,265 217 269 1,751
2007 1,311 152 224 1,687
2008 1,114 130 196 1,440
2009 1,044 96 215 1,355
2010 850 97 183 1,130
2011 757 78 143 978
2012 798 98 134 1,030
2013 800 62 164 1,026
2014 786 74 129 989
2015 760 80 146 986
2016 723 68 133 924
2017 697 91 120 908
2018 687 86 99 872
2019 640 95 135 870
2020 444 71 69 584
2021 499 72 53 624
2022 493 59 58 610
2023 446 66 56 568
Total 25,390 3,133 4,735 33,258

The rolling average chart shows more clearly the downward trend and levelling off. In the time period examined, the SIs reached their highest level in the period 2000-2002 (average SIs = 226), after which the numbers started to fall. The temporary rise in 2006 is, however, still evident. The smoothed trend, which showed large reductions earlier in the series, began to show a slower rate of reduction from 2010 onwards, with a gradual increase from 2013-2015 to a slight peak in 2017-2019. However, since then the figures have gradually decreased again. The latest 3 years, 2021-2023 had an average number of 66 SIs, which is the lowest in the series, a reduction of over seven-tenths (71%) on the series peak.

MAIS 3+ compared with police-reported data

Table 1: Admissions to hospital for road traffic collisions and PSNI reported Serious Injuries:
Northern Ireland, 1999-2023
Year Number of Admissions1 MAIS 3+ MAIS3+/ Admissions PSNI Serious Injuries MAIS3+/ PSNI SIs PSNI SIs/ Admissions
1999 2,429 204 8% 1,509 14% 62%
2000 2,409 210 9% 1,786 12% 74%
2001 2,405 234 10% 1,682 14% 70%
2002 2,290 235 10% 1,526 15% 67%
2003 1,865 185 10% 1,288 14% 69%
2004 1,833 195 11% 1,183 16% 65%
2005 1,695 178 11% 1,073 17% 63%
2006 1,751 217 12% 1,211 18% 69%
2007 1,687 152 9% 1,097 14% 65%
2008 1,440 130 9% 990 13% 69%
2009 1,355 96 7% 1,035 9% 76%
2010 1,130 97 9% 892 11% 79%
2011 978 78 8% 825 9% 84%
2012 1,030 98 10% 795 12% 77%
2013 1,026 62 6% 720 9% 70%
2014 989 74 7% 710 10% 72%
2015 986 80 8% 711 11% 72%
2016 924 68 7% 828 8% 90%
2017 908 91 10% 778 12% 86%
2018 872 86 10% 730 12% 84%
2019 870 95 11% 774 12% 89%
2020 584 71 12% 596 12% 102%
2021 624 72 12% 809 9% 130%
2022 610 59 10% 910 6% 149%
2023 568 66 12% 880 8% 155%
1999-2023 33,258 3,133 9% 25,338 12% 76%
2019-2023 3,256 363 11% 3,969 9% 122%
* 1. A single patient may have more than one admission of care arising from a single collision; however, the number of such cases is expected to be very small.


Of the 33,258 hospital admissions in Northern Ireland for road traffic collisions between 1999 and 2023, only 3,133 (9%) were classified as seriously injured based on the MAIS 3+ definition. In the most recent five years, 2019-2023, it was 11%. It should be noted that the MAIS score was unknown in 11% of cases, so the true number of admissions with a MAIS 3+ may be significantly higher. See table 1 above.

The number of MAIS 3+ casualties in Northern Ireland is much lower than the number of seriously injured casualties reported by PSNI; over the 25-year period 1999-2023 the numbers of MAIS 3+ casualties accounted for 12% of PSNI serious injuries (see table 1). In 2019-2023, this decreases to 9%. This reflects the higher severity threshold for a serious injury on the MAIS scale offset, to a certain extent, by the PSNI under-reporting issue.

In general, PSNI defines a serious injury1 as one for which a person is detained in hospital as an ‘in-patient’ or if they have one or more injuries from a predefined list. Since 1999, the total amount of PSNI SIs was 25,338, and by contrast, admissions to hospital for road traffic collisions in the same period was 33,258. This highlights the fact (mentioned previously) that there is a significant proportion (around a quarter) of SI casualties not known to the police. This under-reporting issue has been noted across many jurisdictions including Great Britain and the Republic of Ireland. The most recent year has shown the highest level of reporting, for the fourth year in a row, there were more PSNI SIs than hospital admissions, with PSNI SIs being 55% higher than hospital admissions.

Figure 2: MAIS 3+ road casualties following a road traffic collision compared with PSNI reported Serious Injuries: Northern Ireland, 1999-2023
Single y-axis
Secondary y-axis
Data
Year MAIS 3+ PSNI Serious Injuries
1999 204 1,509
2000 210 1,786
2001 234 1,682
2002 235 1,526
2003 185 1,288
2004 195 1,183
2005 178 1,073
2006 217 1,211
2007 152 1,097
2008 130 990
2009 96 1,035
2010 97 892
2011 78 825
2012 98 795
2013 62 720
2014 74 710
2015 80 711
2016 68 828
2017 91 778
2018 86 730
2019 95 774
2020 71 596
2021 72 809
2022 59 910
2023 66 880
1999-2023 3,133 25,338
2019-2023 363 3,969

In Figure 2 the overall trends can be compared between the PSNI SIs and MAIS 3+ casualty numbers. Notwithstanding the difference in the levels of casualties reported by each definition, it is noteworthy that both series have shown a historic decrease followed by signs of levelling off in recent years. The large peak seen in MAIS 3+ casualties in 2006 was echoed in the PSNI data; however, the greater variability associated with the much smaller numbers of MAIS 3+ casualties mean its peak is more pronounced. Since 2020, there has been a contrast in trend between PSNI SIs and MAIS3+ casualties. When one has seen a decrease from the year before, the other has seen an increase; and vice versa.

Analysis of MAIS 3+ casualties

The following analysis looks at MAIS 3+ casualties in the last 5-year period (2019-2023).

Sex

Figure 3: Proportion of MAIS 3+ casualties by sex: Northern Ireland, 2019-2023
Infographic

Data
Year Hospital Admissions: Male Hospital Admissions: Female Hospital Admissions: Total Hospital Admissions: % Male MAIS3+: Male MAIS3+: Female MAIS3+: Total MAIS3+: % Male PSNI: Male PSNI: Female PSNI: Total PSNI: % Male
2019 558 312 870 64% 68 27 95 72% 484 290 774 63%
2020 409 175 584 70% 50 21 71 70% 384 212 596 64%
2021 421 203 624 67% 45 27 72 63% 499 310 809 62%
2022 423 187 610 69% 46 13 59 78% 556 354 910 61%
2023 368 200 568 65% 41 25 66 62% 551 329 880 63%
1999-2023 22,294 10,963 33,258 67% 2,234 899 3,133 71% 13,151 7,210 20,361 65%
2019-2023 2,179 1,077 3,256 67% 250 113 363 69% 2,474 1,495 3,969 62%


Males accounted for nearly seven-tenths (69%) of the total MAIS 3+ casualties in Northern Ireland in the five years from 2019 to 2023. This is greater than the proportions of male casualties reported in overall hospital admissions (67%) and PSNI serious injuries (62%).

Age

Figure 4: Proportion of casualties by age2: Northern Ireland, 2019-2023
Chart
Data
Age Band MAIS3+ MAIS3+ % PSNI PSNI % Hospital Admissions Hospital Admissions %
0-9 11 3% 151 4% 243 7%
10-19 45 12% 617 16% 447 14%
20-29 53 15% 755 19% 534 16%
30-39 34 9% 581 15% 430 13%
40-49 38 10% 476 12% 368 11%
50-59 46 13% 568 14% 450 14%
60-69 40 11% 391 10% 313 10%
70+ 96 26% 430 11% 471 14%

More than a quarter (26%) of MAIS 3+ casualties from 2019-2023 were aged 70 and over. This differs markedly from the age profile of overall hospital admissions for road traffic collisions and PSNI serious injuries, where 14% and 11%, respectively, were in this age band. The high proportion of MAIS 3+ casualties which were aged 70 and over is perhaps not surprising given people in this age band are likely to be more vulnerable than those who are younger, and you may expect an older person would suffer more serious injuries if in a collision.

When looking at the full trend of available data (1999-2023 for hospital admissions; 2002-2023 for PSNI SIs), the proportions for all casualties are lower, with 17% of MAIS 3+ casualties falling within the 70+ category, compared with 9% for hospital admissions and 8% for PSNI SIs. The greater differences observed more recently is largely a result of decreases in the number of MAIS3+ casualties aged 10-39 alongside increases in numbers for those aged 70+ – see figure 5 below.

Figure 5: MAIS 3+ casualties by age at start of admission: Northern Ireland, 1999-2023 (Selected age bands)
Chart
Data
1999 - 2001 2000 - 2002 2001 - 2003 2002 - 2004 2003 - 2005 2004 - 2006 2005 - 2007 2006 - 2008 2007 - 2009 2008 - 2010 2009 - 2011 2010 - 2012 2011 - 2013 2012 - 2014 2013 - 2015 2014 - 2016 2015 - 2017 2016 - 2018 2017 - 2019 2018 - 2020 2019 - 2021 2020 - 2022 2021 - 2023
0-9 18 14 12 11 9 9 9 9 9 9 7 6 4 3 1 2 2 3 2 2 2 2 3
10-19 52 54 53 44 41 51 49 43 24 19 16 14 12 11 9 9 9 10 11 12 11 9 8
20-29 47 50 48 48 42 42 37 34 28 22 16 15 12 13 12 11 11 11 16 15 13 9 8
30-39 30 35 33 31 26 25 23 18 17 13 12 10 9 7 5 4 6 6 8 6 7 5 7
40-49 18 17 16 16 17 20 20 18 15 12 11 11 10 10 10 10 9 9 9 8 7 8 7
50-59 12 16 16 16 12 14 13 12 7 7 6 9 10 9 10 10 13 13 13 11 10 8 9
60-69 10 11 13 15 16 13 9 9 6 7 6 8 8 9 7 7 6 6 7 9 9 9 7
70+ 28 30 28 25 24 23 23 23 20 20 17 17 15 16 18 20 24 24 26 22 19 17 18
Total 216 226 218 205 186 197 182 166 126 108 90 91 79 78 72 74 80 82 91 84 79 67 66

At the start of the reporting period, the numbers of MAIS 3+ casualties aged 10-29 were much greater than of those aged 70+, while those aged 30-39 were just slightly above. All four groups have seen a decline over the time series; however, the number of older person casualties did not fall to the same extent as numbers in other age groups, and in 2013-2015 started to increase to an average of 26 recorded in 2017-2019, before falling to 18 in 2021-2023. The result is that numbers of casualties aged 70+ are now greater than those in the younger three groups. It can be seen that the large spike in casualty numbers mentioned previously, which appeared in 2006, was caused by the ‘Aged 10-19’ group. Additionally, the increase in MAIS3+ casualties from 2016-2018 to 2017-2019 are largely explained by increases in MAIS 3+ casualties in the ’Aged 20 to 29’ group (numbers in this category have risen by an average of 5 - from 11 to 16).

Looking at both age and sex, males aged 70+ accounted for the greatest proportion of overall MAIS 3+ casualties in 2019-2023 (15%); with males aged 20-29 (12%) and females aged 70+ (11%) second and third.

Looking at the PSNI data – there we see young male casualties are the most frequently reported (12% aged 20-29), with far fewer in 70+ age category. In both trends, we see that the proportion of male casualties far exceeds females for the younger age groups; indeed, the proportion of male casualties is higher for every age-band. See figure 6 below.

Figure 6: Age and Sex of casualties: Northern Ireland, 2019-2023
MAIS3+ Casualties
PSNI SIs
Data
Age Band MAIS3+ Male % MAIS3+ Female % MAIS3+ Total % PSNI Male % PSNI Female % PSNI Total %
0-9 2% 1% 3% 2% 1% 4%
10-19 9% 3% 12% 9% 6% 16%
20-29 12% 3% 15% 12% 7% 19%
30-39 7% 3% 9% 10% 4% 15%
40-49 8% 2% 10% 8% 4% 12%
50-59 9% 4% 13% 9% 5% 14%
60-69 7% 4% 11% 6% 4% 10%
70+ 15% 11% 26% 6% 5% 11%

Road user type

Figure 7: MAIS 3+ casualties compared with PSNI reported seriously injured casualties, by road user type: Northern Ireland, 2019-2023
Chart

Data
Road User MAIS3+ Number MAIS3+ % PSNI Number PSNI %
Pedestrian 68 19% 764 19%
Pedal Cyclist 49 13% 312 8%
Motorcyclist 41 11% 494 12%
Car 155 43% 2,264 57%
Other/Unknown 50 14% 135 3%
Total 363 100% 3,969 99%


Figure 7 above shows a comparison of MAIS 3+ casualties with PSNI serious injury casualties, by road user type, over the period 2019-2023. As expected, the most frequently recorded road user type of the MAIS 3+ casualties was car users (43%). However, the equivalent proportion of PSNI Serious Injuries is 57%. Therefore, the numbers of casualties that were travelling by the more vulnerable modes (pedestrian, motorcycle and pedal cycle) made up a greater proportion of the MAIS 3+ total than they did of the PSNI SIs (44% compared with 40%, respectively). Like the over-representation of older people in the MAIS 3+ numbers, this again is not surprising: you might expect that a motorcyclist or cyclist, for example, would suffer injuries at the more severe end of the scale if in a collision than someone travelling by car. However, it should also be noted that research conducted in Great Britain has shown that there is significant under reporting of non-fatal pedal cyclist casualties in police data and it would not be unreasonable to assume this would also be the case in Northern Ireland, and which may also help to explain at least part of the difference.

Figure 8: Admissions to hospital for road traffic collisions by road user type and severity: Northern Ireland, 2019-2023
Chart

Data
Road User MAIS 3+ MAIS 1-2 MAIS Unknown Total
Pedestrian 68 406 40 514
Pedal Cyclist 49 492 28 569
Motorcyclist 41 328 19 388
Car 155 1,026 237 1,418
Other 29 163 17 209
Unknown 21 107 30 158
Total 363 2,522 371 3,256


Figure 8 shows the admissions to hospital in Northern Ireland for road traffic collisions, split by road user type and severity of injury. Of the admissions between 2019-2023, 11% were MAIS 3+, 77% had a MAIS score of 1 or 2 with the remaining 11% having unknown MAIS. This differs slightly by road user type, with Other having the greatest proportion of admissions that were MAIS 3+ (14%) and pedal cyclists the fewest (9%). This analysis, however, is somewhat confounded by the high percentage of unknowns across the various road user categories; in particular car user admissions, where 17% were unclassified, over double the proportion of the more vulnerable road user groups. It is currently unclear why such a high proportion of car user admissions have been unable to be classified by the MAIS 3+ measure.

Figure 9: Number of MAIS 3+ casualties by road user type: Northern Ireland, 2019-2023
Annual trend
Rolling average trend
Data
Year Pedestrian Pedal Cyclist Motorcyclist Car Other Unknown Total
1999 57 12 16 92 7 20 204
2000 48 12 35 92 13 10 210
2001 49 6 37 118 12 12 234
2002 41 13 36 123 6 16 235
2003 29 5 35 97 4 15 185
2004 25 13 28 96 11 22 195
2005 22 8 40 79 11 18 178
2006 50 17 40 75 14 21 217
2007 22 7 27 72 9 15 152
2008 23 8 24 60 5 10 130
2009 16 10 20 38 6 6 96
2010 21 11 20 37 2 6 97
2011 23 7 13 27 5 3 78
2012 20 14 14 41 7 2 98
2013 10 8 11 28 3 2 62
2014 7 14 9 37 6 1 74
2015 14 4 14 43 3 2 80
2016 15 10 8 27 6 2 68
2017 18 10 11 46 2 4 91
2018 14 13 13 35 7 4 86
2019 18 10 15 39 6 7 95
2020 9 17 5 29 6 5 71
2021 13 5 6 36 4 8 72
2022 16 12 6 19 6 0 59
2023 12 5 9 32 7 1 66

When looking at the number of MAIS 3+ casualties by road user type for the most recent five years, it’s clear that each series experiences year-on-year volatility exacerbated by the small numbers in these sub-groups. For that reason, the rolling average chart has been included to give a clearer indication of which direction the trends are moving. The smoothed trend would suggest there has been little change over the years to Pedal Cyclist MAIS 3+ casualties (the moving average tends to regress to a mean of 10 casualties); however, this must be seen in light of an increased level of cycling over largely the same time period (average miles cycled per person per year in Northern Ireland has doubled over the 15 year period 2002/04 to 2017/19, from 17 miles to 34 miles respectively)3. The three other main road user types have all experienced varying degrees of decline. Car User numbers have experienced the greatest decrease, from 113 casualties, on average in 2001-03, to 29 in 2021-23.

Methodology

The AIS

When a patient is admitted to hospital, clinical details of their conditions are coded to the International Classification of Diseases 10th revision (ICD-10) . A standard look-up table has been developed by the European Commission to convert the ICD-10 diagnostic codes of road traffic related hospital admissions to the Abbreviated Injury Scale (AIS). This then provides for international comparisons of road traffic serious injuries on a consistent basis.

The AIS severity score is an ordinal scale of 1 to 6 (1 indicating a minor injury and 6 being unsurvivable) developed by the Association for the Advancement of Automotive Medicine (see table below). An admission to hospital may have a number of different injuries, with differing severities. The Maximum Abbreviated Injury Scale (MAIS) is therefore the AIS score of the most severe injury that a patient sustains; if a patient has one injury with an AIS score of 2 (moderate) and another with AIS of 4 (severe) then their MAIS score is 4. Patients with a MAIS of 3 or above (MAIS 3+) are considered to be clinically seriously injured.

Abbreviated Injury Scale

AIS Code Injury Example
1 Minor Superficial laceration
2 Moderate Fractured sternum
3 Serious Open fracture of humerus
4 Severe Perforated trachea
5 Critical Ruptured liver
6 Unsurvivable Total severance of the aorta
9 Not Known

Producing the MAIS 3+ numbers used in this report

In addition to providing details of the injuries sustained, the ICD-11 codes also provide information on how a patient’s injuries were caused. Hospital patients who have an external cause of injury relating to a road transport collision (codes V01 to V89, excluding V81) were extracted from the hospital admissions inpatient database over 1999 to 2023. Only casualties whose injuries related to collisions that occurred on a public highway (i.e. road traffic collisions) were included. Each admission was therefore assigned to a MAIS category as follows: - MAIS 3+ if any of the patient’s codes were AIS 3 or above - MAIS<3 if all of the patient’s codes were AIS1-2 - Unknown if all of the patient’s codes were unknown - Unknown if none of the patient’s codes were AIS 3 or above and at least one code was unknown

Accompanying Tables

To download an Excel document containing the accompanying tables for this publication, click the download button below:

Clinically seriously injured (MAIS3+) road casualties in Northern Ireland, 1999-2023 Tables

Contact Details

Published by: Analysis, Statistics and Research Branch

Lead Statistician: Jonathan Irwin

Telephone: 028 90 346 270

Email: asrb@nisra.gov.uk

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