That is a tremendously good letter. It does a number of things that probably can't be done often enough.
* it reminds everyone of the scale of death and injury caused by road accidents through the comparison with the number of murders
* it links speeding to risk, injury and death (i.e. not harmless) and enforcement to safety (not a cash generator or 'war' on motorists)
* it identifies safety as a high priority to local concerns and policing as a response to that
* that accidents need to be actively avoided.
It seems to be about changing attitudes to what is acceptable. I saw an old drink driving advert, from 1972 I think, with the slogan "Don't have that fifth pint". FIFTH! Continual restatement and reduction of what is acceptable gets us to the point where one pint is now a worry.
And enforcement. Testing and prosecuting drunk drivers was always important and a belief that there was now a higher probability of being caught over the limit was a key factor in reducing the level of drunk driving. But I think the shift in attitudes was much more important in achieving general compliance. Being done for drink driving shifted from being tough luck to being more like a public confirmation that you have a drink problem. From an inconvenience to something shameful.
And so with speeding. The priority needs to shifting attitudes rather than enforcement. Of course, there needs to be more enforcement. People need to believe that there's a high probability of being caught but they also need to feel that being caught speeding would be shameful and at the moment it isn't.