The below charts show how the reliability of services on the Severn Beach Line has changed since May 2017. This includes cancellations, and groups the short-delay trains (1-4 minutes) with on-time trains.

We’ve reverted to one bar chart for period since May 2017, in order to better view the increase in services since the December 2021 timetable “uplift”.

Scroll to the bottom of the graph to see noteworthy causes of disruption/improvement over the years.

Severn Beach Line Reliability - since May 2017
Severn Beach Line Reliability – since May 2017

Noteworthy causes of service disruption/improvement since January 2020:
February 2022 – blockade of Severn Beach Line for Clifton Tunnel & Portway P&R engineering – Sat 19th-Sun 27th Feb
February 2022 – 68 of the 80 February cancellations were due to widespread GWR suspension of services for Storms Dudley & Eunice on Friday 18th February
December 2021 – timetable upgrade on 12th December to a theoretical 448 services per week (from 316), but Covid-related driver shortages resulted in cancellations and reduced timetable
August 2021 – Bristol East Junction engineering over-run on weekend of 14th/15th August resulted in 56 cancellations
July/August 2021 – Bristol East Junction engineering from 10th July-3rd September, on some Sundays services replaced by buses, on some days services terminated/started at Lawrence Hill
January 2021 – announcement of lockdown #3 from January 5th onwards, GWR says it will continue to run the December temporary timetable
December 2020 – new timetable with later services on Sunday mornings for Temple Meads engineering, also GWR staff shortages due to Covid-19 result in temporary timetable over Xmas and new year
November 2020 – announcement of lockdown #2  from November 5th-December 2nd
July 2020 – full timetable resumed from Saturday 11th July with 46pd on Saturdays – passenger numbers rising
May 2020 – service increased from Sunday 17th May – 26pd Sunday, 32pd Saturdays, 50pd weekdays, still very low passenger numbers due to Covid-19
April 2020 – official Covid-19 timetable introduced Monday 30th March – service reduced to 26pd Sunday, 32pd Saturdays, 26pd weekdays (28pd weekdays from 13th April)
March 2020 – at least 118 of these 134 cancellations were “planned cancellations”  for GWR interim emergency Covid-19 timetable from 23-27th March (start date of lockdown #1)
Noteworthy causes of service disruption/improvement for May 2017 to December 2019:
December 2019 – increase in IET London service frequency
December 2018 – services are routed via four-tracks on Filton Bank
Autumn 2018 – Filton Bank blockade 27th October to 18th November plus weekends of 13th/14th Oct, 24th/25th Nov, 1st/2nd Dec
Summer 2018 – several weekends of engineering bustitution
July 2018 – Network Rail complete BASRE/ARS tweaks to improve SBL regulation
Spring/Summer 2018 – GWR introduce measures to improve Turbo 166 performance on SBL, e.g. intermediate door controls
April 2018 – Network Rail (NR) complete Bristol Area Signal Renewal & Enhancement with some disruption to SBL services
March 2018 – SBL problems due to snow
July 2017 – issues with introduction of Turbo 166s

“Late” =  services 5 or more minutes late on arrival at Severn Beach Line destination northbound, or Severn Beach Line destination southbound, ie, not beyond Bristol Temple Meads
“Cancellations & turnbacks” =  includes services cancelled throughout,  services turned back prior to (or started after) scheduled stations and services that skipped scheduled stops
“On Time” = services run to time or less than 5 minutes late
This data has been collected variously from realtimetrains, raildar and recenttraintimes, none of which guarantee 100% accuracy.  (AM/TM/CJD)
Number of services run per month depends on month length, weekdays in a month, extra summer Sunday services and scheduled timetable changes for engineering