Our ref:
620612
Simon Sheldon-Wilson
Your ref:
Divisional Director
ID Customer Solutions
C6/05 Broadway
HMP Britain
Broad Street
[FOI #17723 email]
Birmingham B15 1BL
16 October 2009
Dear Sir or Madam
INTERNAL REVIEW OF YOUR FOI REQUEST
I am writing in response to your request of 21st September 2009 for a review of our
response to your original Freedom of Information request dated 6th September.
In our letter we incorrectly recorded the data of your letter as 6th December when it was
in fact 6th September. Additionally the phrase ‘[Delete where appropriate]’ was
inadvertently left within the letter. Please accept my apologies for the oversight that led
to these inaccuracies.
With regards to your request and our review I can confirm that the Highways Agency
does hold most of the information you requested. I have decided that some of this
information can be released and that other information should not.
Your letter stated
“3. I requested 'more information about [the process of
hashing]'. I expected this to include but not be limited to the exact hashing
algorithm”.
We do hold information on this but a decision has been taken not to release the data
under section 31(1) of the Freedom of Information Act 2001 – see the attached Public
Interest Test at Annex B.
Your letter stated
“4. In relation to point 3, I requested any document or index of
documents that details the process of hashing. This has not been provided”.
We do hold documentation on this but a decision has been taken not to release the data
under section 31(1) of the Freedom of Information Act 2001 – see the attached Public
Interest Test. I can confirm that the Highways Agency do not hold an index of this
documentation.
620612 Internal review response
Page 1 of 5
Your letter stated
“5. On the point of helping police with enquiries, I fail to see how-
-if this data is classed as non-personal data and hashed appropriately--that you
would be able to help the police with their enquiries. I am keen to hear how you
are able to help the police in a meaningful capacity and eager to hear more. An
index of documents is fine”.
The Highways Agency will, from time to time, provide assistance to the Police in the
investigation of specific serious crimes. Where it is the case that assistance can be
provided, then the Police may work with the Agency to recreate a hashed tag of a
specific vehicle registration number created using the known algorithm. The police will
also provide a defined location and time period.
The hashing process creates a non-unique tag that may consequently apply to a
number of vehicles. The Highways Agency cannot therefore be definitive about a
specific vehicle, and can only say whether or not one or more vehicles with that tag was
observed at the location and within the specified time parameters.
I can also confirm that we do not hold an index of documents.
Your letter stated:
“6. You give the impression in your response that the VRN data
is hashed at the camera site into a non-unique tag and sent to the National Traffic
Control Centre and then to Traffic Information Services. Could you please confirm
these are the only recipients of the tags, and that this data--with a different
hashing algorithm or without one at all--is not also sent somewhere?”.
In response to point 6 I can confirm that the National Traffic Control Centre operation is
the only recipient of the tags.
The information being withheld in relation to your points 3 and 4 falls under the
prejudice to law enforcement exemption in section 31(1) of the Freedom of
Information Act 2000.
In applying this we have had to balance the public interest in withholding the information
against the public interest in disclosure.
The attached annex A to this letter sets out the exemption in full and details why the
public interest test favours withholding the information can be seen in Annex B.
The information provided will now be published on our website together with any related
information that will provide a key to its wider context.
If you are not content with the outcome of the internal review, you have the right to
apply directly to the Information Commissioner for a decision. The Information
Commissioner can be contacted at:
Information Commissioner’s Office
Wycliffe House
Water
Lane
Wilmslow
Cheshire
620612 Internal review response
Page 2 of 5
SK9
5AF
If you have any queries about this letter, please contact me. Please remember to quote
the reference number above in any future communications.
Yours sincerely
Simon Sheldon-Wilson
Divisional Director
[[email address]]
620612 Internal review response
Page 3 of 5
Annex A
Request for ANPR hashing algorithm
Exemption applied – Section 31 – prejudice to law enforcement
Factors supporting disclosure
Factors supporting non-disclosure
There is a public interest in
Disclosure of the hashing
understanding the nature of the
algorithm would show how each
hashing process so that the
unique tag is created. With this
public can understand how their
knowledge registration plates
personal data is protected. There
could be manipulated to create
is currently a general public
artificial tags.
interest in government’s
The hashing process is used to
operation of cameras and the
provide maximum protection to
use of information captured on
personal data as required by the
these cameras. Release of the
7th Data Protection Principle of
algorithm would help to
the Data Protection Act. The
contribute to the public debate
release of any part of this
ANPR cameras are installed for
process weakens that protection.
the purposes of journey time
ANPR cameras are primarily
calculation through anonymous
concerned with capturing journey
data and there should therefore
time data and used for traffic
be no barrier to disclosing their
modelling and this is used for
functionality.
widespread public benefit. In
some specific circumstances the
raw data can be used by the
Police to assist with enquiries into
specific incidents. A greater
understanding of the nature of
this assistance would make it
possible for those intent on
criminal behaviour to understand
how such evidence can be
avoided. It is not in the public
interest to prevent this assistance
to the Police.
Conclusion: the Public Interest test shows that the public interest is in withholding
the information
Date of PIT: 9th October 2009
620612 Internal review response
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Annex B
31 Law enforcement
(1) Information which is not exempt information by virtue of section 30 is exempt
information if its disclosure under this Act would, or would be likely to, prejudice—
(a) the prevention or detection of crime,
(b) the apprehension or prosecution of offenders,
(c) the administration of justice,
(d) the assessment or collection of any tax or duty or of any imposition of a similar
nature,
(e) the operation of the immigration controls,
(f) the maintenance of security and good order in prisons or in other institutions where
persons are lawfully detained,
(g) the exercise by any public authority of its functions for any of the purposes specified
in subsection (2),
(h) any civil proceedings which are brought by or on behalf of a public authority and
arise out of an investigation conducted, for any of the purposes specified in subsection
620612 Internal review response
Page 5 of 5
