GeraClinic / A&E Waiting Times Index / Methodology
How the Gera A&E Waiting Times Index is calculated
The Gera A&E Waiting Times Index is a reproducible 0–100 score derived entirely from the real NHS England A&E Attendances and Emergency Admissions release. This page sets out the exact formula, the weights, the two disclosed reference ceilings, a worked example, the data provenance and the limitations — so anyone can reproduce or challenge the number.
What the index measures
The index answers one question: how long do patients wait in a major (Type 1) A&E department? It blends two official NHS A&E accountability metrics into a single 0–100 number, where 0 means almost everyone is seen within 4 hours with virtually no 12-hour waits, and higher means longer waits. It is published nationally, for 118 named Type-1 A&E providers and 7 NHS England regions, so the same number is comparable across every cut.
Direction of the score: higher = longer waits (worse). This is the opposite direction to the Gera NHS Waiting Times Index for elective (RTT) care, where higher = shorter waits. Each index states its direction explicitly on every page.
The formula
1. Breach component (B) — weighted 60%
The share of major (Type 1) A&E attendances not seen, admitted or discharged within 4 hours, scored against a 50% reference ceiling — the breach rate at which this component maxes out. Half of all major-A&E patients waiting over 4 hours is a documented crisis level. For context, the NHS operational standard is that 76% of all attendances are dealt with within 4 hours.
breachRate = t1over4 / t1att
B = min(100, breachRate / 0.5 × 100)
2. Trolley component (T) — weighted 40%
12-hour “trolley waits” — patients waiting 12+ hours from a decision to admit (DTA) to actually being admitted — per 1,000 major (Type 1) attendances, scored against a ceiling of 100 per 1,000 (i.e. 10% of major attendances becoming a 12-hour trolley wait). This is the long-wait severity metric that dominates winter-crisis reporting.
trolleyPerK = wait12 / t1att × 1000
T = min(100, trolleyPerK / 100 × 100)
3. The blended index (GAWTI)
GAWTI = 0.6 × B + 0.4 × T (rounded to 1 dp)
The 0.6/0.4 weighting is a documented Gera editorial choice: the 4-hour breach is the headline wait, and the 12-hour trolley tail acts as a severity modifier. Higher = longer waits. Both reference ceilings (50% and 100 per 1,000) are disclosed constants — the only editorial choices in the index.
Why this is not the same as the A&E Pressure Index
The Gera A&E Pressure Index multiplies the breach rate by attendance volume, so it ranks the biggest, busiest failing hospitals to the top — it measures the scale of the problem. The A&E Waiting Times Index here is deliberately volume-independent: it measures the wait an individual patient experiences, so a small hospital with dreadful waits scores as badly as a large one. The two answer different questions and are cross-linked, not duplicated.
Worked example — England, March 2026
- Type 1 attendances: 1,451,010, of which 523,986 waited over 4 hours (36.1%)
- 12-hour DTA waits: 46,665 = 32.2 per 1,000 attendances
- B = min(100, 0.361 / 0.5 × 100) = 72.2
- T = min(100, 32.2 / 100 × 100) = 32.2
- GAWTI = 0.6 × 72.2 + 0.4 × 32.2 = 56.2 / 100
Type 1 4-hour performance for context: 63.9% of major-A&E patients were seen within 4 hours (the complement of the breach rate).
Data provenance
Every figure the index consumes is taken directly from the NHS England A&E Attendances and Emergency Admissions Monthly Statistics provider-level release. National figures use NHS England’s published England total; regional figures are the transparent sum of the named Type-1 providers in each NHS England region. No value is estimated or imputed; the index is the only Gera-computed layer, and it is fully specified above.
Contains public sector information published by NHS England and licensed under the Open Government Licence v3.0. Source: NHS England — A&E Attendances and Emergency Admissions, Monthly Statistics (March 2026, published 14 May 2026).
Contains public sector information published by Gera Systems and licensed under the Open Government Licence v3.0 (source data). Source: Gera A&E Waiting Times Index — derived from NHS England A&E open data (March 2026, published 3 July 2026).
What the index does NOT show
- It covers England only, and only major (Type 1) A&E departments — not minor-injury or urgent-treatment units on their own.
- It does not cover ambulance handover delays, waits to be seen by a specialty after A&E, or your personal wait on any given day.
- The 4-hour and 12-hour benchmarks are accountability standards, not clinical urgency thresholds; a clinically urgent patient is prioritised regardless of the average wait.
- The index is a monthly summary measure. For a serious or life-threatening emergency, always go to A&E or call 999 — long average waits do not change that.
- This page is information, not medical advice. For any decision about your own care, use NHS 111 or speak to a clinician.
Update cadence
NHS England publishes A&E attendance and 4-hour performance data monthly. Gera recomputes the index on each release. The figures here are for March 2026 and were last recomputed on 3 July 2026.