How the rules work
SafeNight checks every shift against a small, fixed set of roster rules — using shift start and finish times only. No health data, no scores, nothing else. Here is exactly what it checks, and why.
The six rules
Consecutive nights
Working night shift after night shift without a break is the most common unsafe pattern. A night shift is one that starts between 7:00 pm and 4:00 am, or covers at least 3 hours between 10:00 pm and 6:00 am. Nights count as consecutive when the next one starts within 36 hours of the previous one.
- Warning at 3 nights in a row
- Strong warning at 4 nights in a row
Example warning: "Sarah Chen – 4th consecutive night" (strong)
Rest between shifts
The gap between the end of one shift and the start of the next.
- Warning when rest is under 10 h
- Strong warning when rest is under 8 h
Example warning: "James Patel – rest period 8 h" (strong) — a late finish followed by an early start the next morning.
Shift length
Very long shifts on their own are worth flagging, even without other patterns.
- Warning when a shift is longer than 10 h
Example warning: "Jack Wilson – shift length 12.5 h" (warning)
Recovery after a block of nights
After 2 or more consecutive nights, a person needs a proper reset before their next daytime or evening shift.
- Warning when the gap after a night block is under 48 h
Example warning: "Mei Wong – 23.5 h recovery after 2 nights" (warning)
Night → Day within 48 h
A night shift followed closely by an early start (any start between 4:00 am and 9:00 am within 48 hours) — a backwards turn that leaves almost no time to sleep.
- Warning when a night is followed by an early start within 48 h
Example warning: "Emma Thompson – Night → Day within 48 h" (warning)
7-day hours
Total rostered hours in any rolling 7-day window.
- Warning when the total is above 50 h
Example warning: "Tom O'Brien – 60 h in 7 days" (warning)
Warning levels
Every result is shown with its plain-English reason. There are only two levels — no scores, no colours, no ranking of people.
The checker never blocks silently. When a manager moves a shift, the app shows what changed — what was resolved, what new warnings appeared, and the exact reason. Strong warnings hold a move back unless the manager deliberately confirms it, and the warning stays visible afterwards.
Thresholds can be tuned — within limits
Managers can adjust the thresholds to match their ward's agreement, but only inside safe bounds. Every change is recorded in an audit log.
The staff check-in (KSS) — private by design
Staff can optionally note how sleepy they feel on the well-known Karolinska Sleepiness Scale (KSS), a 9-point scale from 1 (extremely alert) to 9 (very sleepy, fighting sleep). It is one tap, takes seconds, and is never required.
KSS answers, hours slept and "fit for this shift" are visible only to the person who entered them. Managers never see them — not as scores, not as summaries, not anywhere. Skipping a check-in carries no penalty, and the rule checker works fully without any check-ins.
The check-in exists so staff can put a number on how they feel for their own benefit, and raise it with their manager or union if they choose. It is never fed into the rules engine or shown as an alert.
What managers see — and never see
Managers see
- Named warnings: who, which shift, and the exact reason
- Ward-level counts only for summaries
- The roster times you imported, with move and undo tools
Managers never see
- KSS sleepiness answers
- Hours slept or "fit for shift" answers
- Any individual health, fatigue or tolerance score
SafeNight is a roster compliance and wellbeing support tool — not a fitness-for-work or clinical decision system.
See it on a real-sized ward
Start a free trial, load the 50-person demo ward, and watch the warnings appear — then move a shift and see the result update instantly.
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