Wiltshire's Misleading Speed Camera Data
Wiltshire & Swindon Safety Camera Partnership - Safety Camera Enforcement - Core Site Information
The baseline figures shown (in red) give the numbers of recorded Fatal, Serious and Slight injuries at each site and the respective numbers for each year following commencement of camera enforcement.
As an example:
A30 The Pheasant, Winterslow:
In the 3 years prior to enforcement, there were 4 serious injuries and 6 slight injuries at that location. In the 7 years and 7 months (more than twice the baseline period) since enforcement commenced, there have been a total of 3 accident collisions which resulted in 4 slight injuries.
(This is cut from http://www.safetycameraswiltshire.co.uk/uplfiles/Core%20Stats.pdf where all the data for all the camera sites is.)
But wait - So we know the red baseline figures for “The Pheasant” is for three years. The presentation misleadingly could be taken that they are an annual figure, as are all the others. The pdf doesn’t seem to say for how long the base data figures are for any other site. Are they all for three years aggregated together?
For clarity wouldn’t annual figures be better? The columns for the start year and the last year of figures are also part years and so are not comparable either.
A masterclass of misleading chartmanship..
UPDATE From The Wiltshire Safety Camera Partnership:
The PDF file which discloses the accident statistics relative to each of
our core enforcement sites is updated as often as possible and certainly
when new (monthly)information comes to hand. The red figures as noted in
the explanation on the relevant page you accessed relate to the three
year period prior to enforcement and these are the figures which were
presented to the Department for Transport for their consideration for
the authorisation to commence enforcement. This is why the figures are
presented in the way they are.
We have listed accident figures year by year to enable anyone who would
wish to aggregate any three year period that they might wish in
comparison with the base line figures. Disclosing annual figures can
also show any trend that might be occurring.
The dates shown in column 3 relate directly to the date enforcement at
the site commenced and the date of the latest statistics update - hence
the last date in all cases is currently 30 November 2009.
The text you refer to was entitled 'As an example' and used the first
site on the list and was intended to imply that the three year period
applied to all sites. However, in light of your comment, I have, this
morning changed the text to that shown below which will hopefully remove
any confusion or misunderstanding.
'The baseline figures shown (in red) give the numbers of recorded Fatal, Serious and Slight injuries at each site for the three year period prior to enforcement commencing. The numbers of injuries for each year following commencement of camera enforcement are also shown.'