The other day I explored some of the possible reasons for the huge increase in serious injury in one year amongst cyclists. 
I put it down partly to an increase in cycle use masked by poor weather the year before, and a steady fall in traffic law enforcement.
That decline in law enforcement is most noticeable in the reduction in police on the streets, but action taken by prosecutors and the courts has also fallen significantly..
The most serious cases - such as dangerous driving or where someone has been killed - are dealt with in the Crown courts.
The magistrates' courts deal with most prosecutions for crimes such as speeding, careless driving. In 2001 this amounted to over 2 million proceedings across England and Wales.
However, by 2011 the number of motoring offences being seen by magistrates had fallen by 56%.
Interestingly these changes were not universal across the board - they varied considerably between police force areas.
Cambridgeshire actually saw a slight increase in findings of guilt, whereas Wiltshire presided over a 72% reduction.
What could explain these variations?
There are a few possible explanations:
- There has been a huge fall in bad driving, meaning that the police and courts have to do less work to bring offenders to justice.
- More offences are being dealt with through Fixed Penalty Notices rather than court action.
- Fewer resources are going into prosecuting cases of bad driving.
To test the first point - have the places with the lowest reductions seen a similarly lower reduction in casualties? (On the basis that casualties are a proxy for bad driving).
Although exactly equivalent data are not available, it doesn't appear as if there has been any link between levels of bad driving and fewer prosecutions. Cambridgeshire has seen a 32% fall in serious and fatal casualties, but a slight increase in findings of guilt, whereas at the other extreme Wiltshire's KSIs fell by 9%. Other police forces - mid-ranking on the table above, saw falls of 1% (Surrey) and 8% (Sussex).
In other words the places with the lowest falls did not necessarily see the biggest reductions in prosecution.
The second point is also likely to be having an effect, because some local authorities have implemented more safety cameras than others, therefore those areas are likely to have seen a fall in magistrates' court prosecutions (where speeding is prosecuted in the absence of camera enforcement).
However, I think it is the third explanation that has had the greatest impact. Fewer resources going into policing has led to huge reduction in prosecution and findings of guilt. In some places road traffic policing and the attendant prosecution of offenders has been a higher priority than elsewhere.