Revisions to road casualty statistics
Updated 30 May 2024
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This publication is available at https://www.gov.uk/government/publications/reported-road-casualty-statistics-background-quality-report/revisions-to-road-casualty-statistics
Overview
Reported road casualty statistics are not routinely revised, with the exception of provisional data, or any figures relating to serious collisions or casualties based on severity adjustments.
Provisional figures are revised as they are finalised. For severity adjustments, separate guidance on the severity adjustments is available, but users should note that they will change with every publication including new data a as result of updates to the model used for the adjustment. Except where a police force has recently adopted injury-based reported, it is not expected that these changes will be large or that there will be notably change in trends for individual police force areas.
This note provides details of any further revisions to previously published figures, by the year in which they were made. Further information is available from the road safety statistics team via the contact details below.
2020: Revisions to historic road casualty data
Alongside the publication of the 2020 reported road casualty figures in September 2021, historic figures for slight and serious injuries were revised from 2012. This section provides further details of this change.
Prior to 2020, whether a casualty was reported as admitted to hospital was factored into casualty severity calculations in the Collision Reporting and Sharing (CRASH) system. From 2020 this is no longer the case. This means that some casualties that would have been reported as ‘serious’ prior to 2020, will be reported as ‘slight’ in 2020 and in subsequent years.
To allow for a consistent comparison of casualty severities between years prior to 2020 and years following this, historic cases since the introduction of CRASH have been updated and corrected to reflect this change.
As a result, some reported casualty severities have been downgraded (from serious to slight) between 2012 and 2019 compared to numbers published in publications up to and including the 2019 annual report. These severity changes affect only casualties reported by police forces that have adopted CRASH. The correction to historic reported casualty severities is only required to be applied once.
Overall, the total number of police-reported ‘serious’ casualties was reduced, and the number of ‘slight’ casualties increased, with respect to previously published figures between 2012 and 2019 because of the corrections applied. However, the overall total number of injured casualties remains unchanged.
The total number of casualties affected is small, with the severity updated for less than 1,500 casualties over all years. The largest impact is for figures in 2019, which includes 572 affected casualty severities. Overall collision severities have also been updated, where appropriate and for the same years, to reflect the changes to casualty severities.
The revisions have been applied to the statistical publications published as part of the 2020 final annual statistics, and to the open data which is made available via data.gov.uk. It is anticipated that from this point on these figures will not be further revised.
2021: Minor historic revisions to casualty road user type
As a result of development of new data tables for the 2021 final annual statistics, a small number of inconsistencies came to light regarding the classification of casualty type in 2015 (where casualty type was not consistent with vehicle type, for vehicle occupant casualties). These inconsistences were corrected, affecting around 100 casualties, with no change in casualty totals.
2021: Minor revisions to contributory factor data
As part of the publication of the 2021 statistics, a small revision was made to data for contributory factors in collisions. This was to identify cases where data for a collision was updated by the reporting police force, but an incorrect version of the contributory factors was taken into the final database. Aside from a handful of records in years 2012 to 2014, this change affected only data for 2019.
Statistics published for contributory factors for 2019 have been revised as a result. While the factors assigned for some collisions have changed, at the aggregate level, the impact on the statistics published (for example in table RAS0701) is small.
2021: Revisions to traffic data used to calculate casualty rates
Following a revision in traffic estimates published by the department’s road traffic statistics team, casualty rates per billion vehicle miles have been revised for the period 2010 to 2020, as part of the publication of the 2021 final annual statistics in September 2022.
As traffic figures have been revised downwards, the impact on casualty rates is a small upwards revision, with the size of the revision greater in 2020 than other years. However, broad trends in casualty rates over time are not affected as a result of this revision.
The revised traffic figures are for minor roads only, so that any casualty rates by road type will show the greatest impact of the revision.
2022: Minor historic revisions for Greater Manchester police force
Following a change of reporting system used by Greater Manchester Police, a small number of records were submitted with incorrect date and time allocated to them when originally published in 2021. These records were updated alongside publication of the 2022 statistics. This change affected less than 35 records in the open dataset and data download tool, but has not impacted on the published statistical reports or tables. Full details of changes can be found in the revision table on the data.gov.uk page.
2022: Minor historic revisions to geographic administration areas and coordinates in Isles of Scilly
Following the continued development of the open data tables, a small number of geographic inconsistencies came to light regarding collisions in the Isles of Scilly for years between 1994 and 2009 which have been revised with the publication of the 2022 statistics. This change affected less than 50 records, and affects only the open dataset. Full details of changes can be found in the revision table on the data.gov.uk page.
2022: Historic population of generic make and model
In the 2002 update of the open data files, the historic back series has been populated with generic make and model for vehicles which have been matched with DVLA data. The generic_make_model field is populated where there are 10 or more instances of vehicle combinations of type, make and model. Vehicle combinations with less than 10 instances are treated as sensitive data, that can be requested from the road safety statistics team.