Great Western Main Line
Last updated 25 May 2026
London Paddington to South Wales via Reading, Swindon, and Bristol — steel, automotive, and intermodal traffic between London and the South Wales ports.
| NR route | Western / Wales & Western |
| Route chain | London Paddington – Reading – Didcot – Swindon – Bristol Parkway – Severn Tunnel Junction – Newport – Cardiff – Swansea |
| Key constraints | Reading area; Severn Tunnel; Cardiff approaches |
| Trailing 12-period A2F | Fewer than 12 closed periods of clean data on record — available once the pipeline reaches 12 complete periods. |
Latest period summary
Great Western Main Line recorded 72% A2F punctuality in Period 2 2026-27 (26 April – 23 May 2026) on 1,117 freight services, down 2 percentage points from 74% in Period 1 2026-27 on a smaller denominator. The intervals overlap with the prior period. PRELIMINARY at T+2; FINAL re-publication at T+35 after Network Rail's batch correction.
Reports
Operators active
Methodology & sources
All figures derive from Network Rail's NROD TRUST feed, processed via the Gauge Intelligence ingest pipeline. Period definitions, A2F (Arrival to Fifteen), the Wilson 90% interval, daily anomaly rules, cross-view reconciliation, and delay attribution are documented at:
Data window — period boundaries and the data-as-of cutoff
League tables — cross-view reconciliation across the four analytical views
Anomaly detection — daily A2F SPC rules
Delay attribution — DAPR cause-code breakdown
Forecasting — prediction intervals and possession-exposure estimates
The Great Western Main Line carries steel, automotive, intermodal, and aggregates flows between the London area, the West, and South Wales. The corridor handles the South Wales steel circuit between Port Talbot, Llanwern, and Margam, intermodal services to and from the South Wales container terminals, and stone trains out of the Somerset quarries via the Chiltern/Aylesbury corridor at Reading.
Capacity at Reading and the single-bore Severn Tunnel are the principal constraints on the route.