I wrote in March about a DVLA dataset, containing counts of licensed vehicles for small areas of the UK based on 2011 Census geography, that the Department for Transport's vehicle statistics team released to me following an FOI request.
Unfortunately, DfT had suppressed values between 1 and 4 in the data based on a view that disclosure of numbers that small "would be likely to lead to identification of individuals if pieced together with other information" – in other words, that the values were personal data.
DfT maintained that position following an internal review, so I submitted a complaint to the Information Commissioner's Office in its capacity as regulator for FOI.
Last month, ICO issued a decision notice supporting my view that the suppressed values were not personal data.
DfT has now supplied the complete table of vehicle counts for Output Areas, calculated to the end of September 2021. You can download the dataset, along with my correspondence with DfT and complaint to the ICO: F0020605 data and docs [20221204].zip.
The data is in the following format:
| OA11CD | Cars | Motorcycles | Others |
|---|---|---|---|
| E00000024 | 80 | 5 | 29 |
| E00042155 | 355 | 6 | 209 |
| E00042425 | 119 | 1 | 6 |
| E00042436 | 53 | 0 | 4 |
| E00167301 | 152 | 8 | 16 |
DfT has confirmed that the dataset has been made available under the Open Government Licence v3.0, without restrictions on re-use of the information. I recommend using the following attribution statement:
Contains public sector information from DfT/DVLA © Crown copyright and database right 2021, licensed under the Open Government Licence v3.0.
In the decision notice, the Information Commissioner referred to the recent Upper Tribunal case NHS Business Services Authority v Information Commissioner and Spivack, which said:
"Identifying a pool that contains or may contain a person covered by the data is not sufficient. Saying that it is reasonably likely that someone is covered by the data is not sufficient. Still less is it sufficient to say that it is reasonably likely that a particular individual may be one of the pool. Linking any specific individual to the data in any of these circumstances does not rely solely on the data disclosed and other data available by reasonable means; it involves speculation."
The Commissioner considered that DFT had failed to demonstrate how an individual could be identified from the data requested:
24. In its submission to the Commissioner the DFT provided a map which displayed two pinpoints that marked two different properties. The DFT advised that these "two specific buildings … will likely be the location of the registered keeper." The Commissioner viewed the map provided and agreed that two buildings are marked by the pinpoints, however the map clearly states that this is an 'active postcode' and goes on to say that there are 'approximately 37 households'. The DFT failed to clearly explain how this map from a third party service would hold and publish the information regarding the location of the owners of vehicles.
25. In this case, the Commissioner considers that the DFT has failed to demonstrate how an individual could be identified from the data requested. Even if an individual was motivated to find the location of an owner of certain vehicles, the Commissioner is unsure how knowing the amount of “Vehicles/Motorcycles/other” in an Output area / Lower Super Output area, would allow for owners to be identified – unless the individual already knew the precise information such as registration of the car, make, model or colour, in which case, disclosure of the withheld information would not tell them anything they did not already know.
If you want to analyse this data in GIS, Output Area boundaries are available from ONS.
If you find the Output Area vehicle counts useful, you will likely also be interested in the small geography data files that DfT has now started to publish. Those include vehicle counts for each quarter back to 2009, by licensing type, body type, and Lower Layer Super Output Area (LSOA). A LSOA is the next largest area of Census geography after the Output Area (OA).
Small numbers are suppressed in those data files also, but I hope DfT will review this practice in light of the recent ICO decision. It seems to me that there is nothing to prevent DfT from publishing its small geography files at OA level, without suppression of values. Increased granularity would enhance the analytic value of this important administrative data.