What causes serious road crashes in Northern Ireland? Latest PSNI data explained
Inattention was the most common principal causation factor recorded for people killed or seriously injured in both the final 2025 data and the first half of 2026. But collision-causation statistics need careful interpretation.
Updated 21 September 2026. Ask what causes serious crashes in Northern Ireland and it is tempting to answer with one word: speed, alcohol, phones or bad roads. The official collision data is more complicated.
In the final 2025 PSNI statistics, the most frequently recorded principal causation factor for people killed or seriously injured was inattention or attention diverted, linked to 115 KSI casualties. “Wrong course/position” was next with 95, followed by “excessive speed having regard to conditions” with 86.
The newest half-year update, covering 1 January to 30 June 2026, again puts inattention or attention diverted first, associated with 85 KSI casualties. Wrong course/position was second with 53 and impairment by drugs or alcohol — driver/rider — was third with 46.
Latest principal causation factors for serious NI collisions
| Period | 1st | 2nd | 3rd |
|---|---|---|---|
| Calendar 2025, final | Inattention / attention diverted — 115 KSI casualties | Wrong course / position — 95 | Excessive speed having regard to conditions — 86 |
| Jan–Jun 2026, provisional | Inattention / attention diverted — 85 KSI casualties | Wrong course / position — 53 | Impairment by drugs or alcohol, driver/rider — 46 |
KSI means killed or seriously injured. The 2026 half-year figures are not directly comparable with a full 12-month total, so the table should be read as two separate snapshots rather than a league table of year-on-year change.
What does “principal causation factor” mean?
Police collision records can include factors considered to have contributed to a crash. The “principal” factor is the one identified as the main recorded causation factor for statistical purposes. A collision can be complex, and one label should not be interpreted as a complete reconstruction of everything that happened.
That distinction is important for SEO articles because phrases such as “the number one cause of crashes” can overstate what the data proves. The safer wording is: the most common principal causation factor recorded in the official data.
1. Inattention or attention diverted
Inattention sits at the top of both the final 2025 and provisional first-half 2026 KSI tables. It is a broad road-safety problem rather than a synonym for mobile-phone use. A driver's attention can be diverted in many ways, and the statistical category should not be narrowed beyond what PSNI has recorded.
That breadth helps explain why distraction-related road safety cannot be reduced to simply enforcing the handheld-phone law. Looking away at the wrong moment, failing to process a developing hazard or becoming mentally disengaged can all matter even where no phone offence is recorded.
2. Wrong course or position
Wrong course/position was the second most common principal factor in both periods: 95 KSI casualties in 2025 and 53 from January to June 2026. The category can capture situations where a vehicle's road position or path is central to the collision.
Again, the data does not justify inventing a specific behaviour for every case. It cannot automatically be translated into “bad overtaking” or “crossing the centre line” without the underlying individual collision records.
3. Speed remains a major severity issue
“Excessive speed having regard to conditions” was the third most common principal factor in the final 2025 KSI statistics, linked to 86 killed-or-seriously-injured casualties.
Separate PSNI road-safety analysis found that excessive speed was a factor in around one in five fatal collisions in 2025. Of 53 fatal collisions, 11 included excessive speed as a factor — seven where it was the principal factor and four where it was contributory.
Those figures matter because speed affects both collision risk and impact severity. A speed can also be inappropriate for the conditions even if it is below the signed maximum limit. The wording used in the statistical factor — “excessive speed having regard to conditions” — is therefore more precise than simply saying “speeding”.
4. Drugs and alcohol moved into the top three in early 2026
For January to June 2026, impairment by drugs or alcohol — driver/rider — was the third most common principal factor for KSI casualties, with 46. That does not mean impairment suddenly became more common than speed over a full year. It means that in this six-month provisional dataset it occupied third place.
The final 2025 Northern Ireland Road Safety Strategy statistics separately recorded nine deaths in collisions where alcohol or drugs was attributed, down from 16 in 2024. That is a different measure from the KSI principal-causation count and should not be merged with it.
How many people were killed or seriously injured?
PSNI's final 2025 statistics recorded 56 fatalities and 1,066 people seriously injured. There were also 6,757 slight injuries. In total, 1,122 people were killed or seriously injured during the year, 11% more than in 2024.
The first six months of 2026 recorded 36 fatalities and 531 serious injuries, giving 567 KSI casualties. That was 62 more KSI casualties than the same six months of 2025, an increase of 12.3%.
Does “human error causes more than nine in ten deaths and serious injuries” mean roads do not matter?
No. Official Northern Ireland road-safety messaging has stated that more than nine in ten deaths and serious injuries are associated with human error, but road design, vehicle safety, speed environment, visibility and other factors can influence whether an error becomes a collision and how severe the outcome is.
Road safety is generally treated as a system problem: safer behaviour, safer speeds, safer vehicles, safer roads and effective post-collision response can all influence outcomes. A driver can make a mistake; the question for a safe system is also whether that mistake results in death or life-changing injury.
Which road users are being seriously hurt in 2026?
Between January and June 2026, PSNI recorded the following KSI totals by broad road-user group:
- Drivers: 222
- Passengers: 113
- Pedestrians: 96
- Motorcyclists: 87
- Pedal cyclists: 24
- Pillion passengers: 3
- Other road users: 22
The numbers are counts, not exposure-adjusted risk rates. There are far more car journeys than motorcycle journeys, for example, so raw casualty counts alone cannot tell you which mode has the highest risk per mile or per journey.
Why short-term figures can mislead
Serious and fatal collisions are thankfully much less frequent than ordinary journeys, which means relatively small changes in the number of crashes can produce large percentage movements over a six-month or one-year period. That is one reason the Department for Infrastructure also tracks longer-term strategy baselines.
For example, 36 deaths in the first half of 2026 were 57% higher than the same period in 2025. That is a serious increase, but it should not automatically be projected forward to predict a full-year total. Seasonal patterns, random variation and future collision numbers can change the final outcome.
What drivers can take from the data
The official statistics do not support one simplistic message. They support several:
- Attention is repeatedly appearing at the top of the serious-collision causation data.
- Road position and course matter in a large number of KSI cases.
- Excessive speed remains strongly connected with fatal-collision severity.
- Drug and alcohol impairment remains a major factor and was in the top three KSI principal factors for the first half of 2026.
- Casualty statistics should be compared over equivalent periods and with the same definitions.
Frequently asked questions
What is the most common recorded cause of serious road crashes in Northern Ireland?
“Inattention or attention diverted” was the most common principal causation factor for KSI casualties in both final 2025 data and the January-to-June 2026 update.
Is speeding the biggest cause?
Not in the principal-factor ranking. It was third in the final 2025 KSI data. However, separate PSNI analysis says excessive speed was a factor in around one in five fatal collisions in 2025, so its importance to fatal-crash severity remains substantial.
How many people were killed on NI roads in 2025?
The final PSNI/DfI figure is 56 fatalities.
How many were seriously injured?
There were 1,066 serious injuries in 2025. From January to June 2026, 531 people were seriously injured.
Sources and data note
- PSNI Road Traffic Collision Statistics
- DfI Northern Ireland Road Safety Strategy annual statistics 2025
The January-to-June 2026 bulletin states that data from 1 April 2026 onward were provisional when published. This article therefore labels them provisional and does not combine six-month figures with full-year totals.
