Workforce & Rostering — Staffing Analysis

From minimum cover to a sustainable ED roster

Naas General Hospital needed to know how many Senior House Officers were required to run its Emergency Department roster sustainably. Modelling the roster itself showed that four SHOs, not three, were needed to meet coverage, rest, hours and leave requirements.

minimum staffing for a workable roster: 3 → 4 SHOs
average working week: 48.8 → 47.6 hrs
for each SHO in a 13-week cycle: 3 weeks leave

The challenge

The ED roster had a relatively simple structure: three weekday shifts, each covered by the same doctor Monday to Friday, and one weekend shift covered by the same doctor on Saturday and Sunday.

With three SHOs available, the department had the minimum number of doctors needed to cover the service on paper. In practice, all three were required every week, leaving no capacity for planned leave; working a weekend meant 12 consecutive days on duty; and average weekly hours reached 48.8.

The question was therefore not “how many doctors do we need to cover the shifts?” but “how many doctors do we need to operate this roster sustainably?”

Our approach

We translated the department's service requirements into a roster model and tested different staffing levels against the practical rules that determine whether a roster works.

Service coverage: ensuring all weekday and weekend shifts could be staffed. Working time: testing against an average 48-hour working week. Rest and consecutive working: avoiding patterns where weekend duties created excessive consecutive days.

Weekend distribution: ensuring doctors were not required to work consecutive weekends. Leave capacity: allowing each SHO at least three weeks' leave during a 13-week roster period.

Rather than estimating the requirement with a simple shift-to-WTE calculation, we generated and tested the roster itself — showing what each staffing level would actually mean for the doctors working it.

What the analysis showed

Four SHOs was the minimum staffing level capable of producing a workable roster under the assumptions tested. Average weekly hours reduced to 47.6, consecutive weekends could be avoided, appropriate rest periods could be provided, and each doctor could receive at least three weeks' leave over the 13-week period.

The model also demonstrated how leave could be positioned before or after a worked weekend to avoid an SHO working 12 consecutive days.

One constraint remained: the four-SHO model generally allowed one doctor to be on leave each week, so multiple simultaneous leave requirements could still create difficulties.

The outcome

The analysis gave the hospital an evidence-based answer to its staffing question. Three SHOs could provide basic cover but could not support a sustainable roster; four provided the minimum staffing level required to create a workable roster under the assumptions modelled.

It also demonstrated why staffing requirements cannot always be determined by counting the shifts that need to be covered. Rest, working hours, weekends and leave can materially change the number of staff required to operate a service sustainably.

A workable four-SHO roster

Sample redesigned Naas ED roster showing four SHOs across weekday, weekend and leave patterns over three weeks — The redesigned roster demonstrated how four SHOs could maintain required ED coverage while providing appropriate rest, managing weekend duties and accommodating planned leave.

Scenario evidence

The model tested staffing levels against the rules that decide whether a roster is workable, not just whether the shifts are covered.

Modelled ED SHO staffing levels

Scenario	Coverage	Average weekly hours	Rest, weekends and leave
3 SHOs	Achieved	48.8	12 consecutive days after a weekend; no capacity for leave
4 SHOs	Achieved	47.6	No consecutive weekends; appropriate rest; 3 weeks' leave per doctor

Key finding

Four SHOs was the minimum staffing level able to deliver ED coverage alongside working-time, rest, weekend and leave requirements.

Outcomes

What changed for the organisation once the platform was live.

4 SHOs
modelled minimum for a workable roster
47.6 hours
average working week at four SHOs
No 12-day runs
leave positioned around worked weekends
No consecutive weekends
designed into the four-SHO model
3 weeks leave
for each SHO in a 13-week cycle
Full ED coverage
weekday and weekend shifts maintained
Evidence for planning
clear basis for the staffing decision
Roster-based method
tested rather than estimated by ratio

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