The hidden severity of overnight road crashes

Road crashes can occur at any time, but their outcomes are not equally severe. This report examines recorded Victorian road crashes between 2012 and 2025, comparing crashes occurring overnight with those recorded during other hours.

For this analysis, overnight refers to crashes recorded between midnight and 5:59 AM, while other hours covers 6:00 AM to 11:59 PM. A severe crash is defined as one classified as fatal or serious injury. The analysis compares the proportion of severe crashes within each time period, rather than the risk of experiencing a crash while travelling.

The central question is: Are overnight crashes consistently associated with more severe outcomes, and does this pattern persist across years, speed zones and road layouts?

This report is intended for Victorian road safety stakeholders and interested members of the public who want to understand how crash severity differs across times of day.

The charts below measure the percentage of recorded crashes classified as fatal or serious injury. These percentages describe crash severity among recorded crashes, not the probability of crashing on a journey.

1. Overnight crashes have a higher share of severe outcomes

Across the recorded crashes, 48.91% of overnight crashes were classified as fatal or serious injury, compared with 36.69% during other hours.

That is a difference of 12.22 percentage points. The finding raises an important question: is this a consistent pattern, or is it driven by particular years?

2. The overnight severity difference persists over time

The overnight group had a higher share of fatal or serious-injury crashes in every year shown, from 2012 to 2025.

In 2018, the overnight severity share reached approximately 56.81%. The smallest difference between the two groups occurred in 2023, at approximately 8 percentage points.

The gap varies, but it does not disappear in the years examined.

3. Speed zones reveal important differences

The overnight severity share was higher in most of the displayed speed zones.

At 60 km/h, 48.45% of overnight crashes were classified as fatal or serious injury, compared with 34.43% during other hours—a difference of 14.02 percentage points.

However, the pattern is not identical in every speed zone. The 90 km/h and 110 km/h comparisons show why it is important to examine individual categories rather than assume the overall finding applies universally.

Interpretation note: The 90 km/h overnight category contains only 35 recorded crashes, of which 15 were classified as fatal or serious injury. Its severe-crash percentage (42.86%) should therefore be interpreted cautiously because it is based on a relatively small number of observations. Differences across speed zones are descriptive associations and do not establish that posted speed limits cause differences in crash severity.

4. The pattern also appears across road layouts

The overnight severity share was higher across all four major road-layout categories shown: cross intersections, T intersections, locations outside intersections, and multiple intersections.

This suggests that the overnight severity difference is not confined to a single type of road layout.

What does the evidence tell us?

The findings point to a consistent association between overnight crashes and more severe recorded outcomes in Victoria.

The pattern appears in the overall comparison, persists across the years examined, and is visible across most speed zones and the major road layouts.

However, these results do not establish that travelling overnight causes more severe crashes. Factors such as traffic conditions, travel speeds, driver behaviour and road environments may contribute to the observed differences.

The key takeaway: Road safety discussions should consider not only how many crashes occur, but also how severe their recorded outcomes are at different times of day.

Data and interpretation

Data source: Department of Transport and Planning, Victoria (2026), Victoria road crash data, Accident CSV. https://opendata.transport.vic.gov.au/dataset/victoria-road-crash-data

Period examined: 2012–2025.

Severity measure: Percentage of recorded crashes classified as fatal or serious injury within each comparison group.

Important limitation: These are proportions of recorded crashes, not crash rates per journey, distance travelled or vehicle exposure.

Interactive features allow readers to inspect individual values and compare groups. The charts were created using R, ggplot2 and Plotly.

References

Department of Transport and Planning. (2026). Victoria road crash data [Data set]. Victorian Government. https://opendata.transport.vic.gov.au/dataset/victoria-road-crash-data