Some interesting figures from 2013
Thames Valley Police recorded 789 crashes involving its patrol cars, with over half of the incidents deemed the fault of the police driver at a cost of £396,000
Surrey Police logged 477 incidents ranging from serious collisions to windscreen chips with repairs to vehicles costing £374,058
Hampshire did far better,with 413 crashes although 300 of the crashes were caused by Hampshire Police personnel, causing damage which cost the force a total of £172,371
Worse was a police officer was killed in one of their crashes.
At least Hampshire defended theirs, the others refused to comment.
Our fleet of vehicles covered 15.8 million miles in all weather conditions in 2012/13 but were involved in an incident where blame can be attributed to the police driver once every 53,000 miles. Although the vast majority of incidents were minor collisions, any incident involving a police vehicle is regrettable.'
The interesting bit I found there was One accident every 53,000 miles. That must work out about the same or worse than an average driver? Ok they often drive in different circumstances, but have extra training to offset that.
Which seems to indicate that human nature is the same and mistakes will be made?
having said all that - the investigation that goes on is quite intensive:
http://www.gloucestershire.police.uk/foi/Information Classes/Policies/item11331.pdf