Note that the driver who killed Jamie Foster was drunk, whilst Darren Jenkins was only three years old, playing in the road. Emotive calls, after such tragedies, for lower speed limits and cameras are common, and even understandable, but I am sure that we can agree that raw emotion is not a good leader for policy. I'd be interested to hear how you think a 20mph limit would have moderated a drunk driver, or a driver who was already allegedly exceeding the 30mph limit. Would the lower number somehow magically garner obedience?
Surely a more common-sense approach would be to target the causal factors, rather than the aggravating ones. Its not okay to accept accidents, so long as they don't kill people, when the opportunity is there to eliminate accidents altogether. We need to treat the disease, not just the symptoms.
I am sure that we would all agree that sometimes 20mph is a safe maximum for tight residential streets, with children playing, poor visibility due to parked cars, etc. In such circumstances one would expect to see the vast majority of responsible drivers (lets say 85% for argument's sake

) driving at or below 20mph and as such it may well be an appropriate limit. Nobody here will disagree with appropriately set limits. The problems arise when limits are not appropriately set, and as such all limits lose a little bit of credibility in the eyes of the driver.