ROD King’s achievement in getting his 20s Plenty pressure group’s publicity all over the place, Guardian letters, August 8, is remarkable. However I’m always suspicious of ‘we know what’s best for you’ organisations since their propaganda is highly selective and ignores facts that don’t support their views, and which merely feeds their beliefs.

Assertion is no substitute for fact. He implies that Warrington’s 2009 pilot study found 20mph limits were highly desirable. That trial, as I’m sure he knows, showed no such thing. The number of casualties actually increased, hardly a ringing endorsement for 20mph limits. No control group, (a basic requirement of any statistical analysis) was used and it was quite naïve to draw any conclusions without this.

The DfT’s statistics covering the years 2011-2013 show the percentage of casualties in 20mph areas increased each year by never less than 16 per cent whereas they fell in 30 and 40 mph areas.

So we can presumably discount weather as a factor. These are percentage not absolute changes so we can also discount Mr King when he claims elsewhere this is because there are more 20mph areas.

On the evidence so far these 20mph limits are not delivering the results that are claimed.

He makes great play of the take up of 20s Plenty in councils across the country. What he doesn’t mention is that in towns like Portsmouth, one of the first to implement these measures, subsequent analysis by independent statisticians questioned the claimed benefits.

Towns like Watford will not consider town wide implementation, and where the public have actually had a say in places like Worthing and York more than 80 per cent rejected them.Who knows what Warringtonians might have said had they been given the chance since as in many areas (like the closure of Sandy Lane tip), our council thinks it knows best and can’t be bothered asking us.

So why, despite the propaganda might accidents increase in 20mph areas? One independent researcher suggests that pedestrians in 20mph areas may feel safer and take less care. At speeds above 40mph pedestrians are likely to be rolled onto or over the roof of a vehicle, at 20-30mph they will be rolled onto the bonnet then thrown forward and away as the vehicle brakes, but at lower speeds the pedestrian is pushed forward down onto the road ahead of the vehicle which then runs over them causing serious injury or death.

It is notoriously difficult to draw statistically significant conclusions from this sort of data.

We need to look far more at actual events and causes rather than just bald statistics. For instance are children or adults involved?

Unfortunately these additional factors are not recorded by the DfT.

Next year assuming WBC is collecting the comparison data, and in the event that casualties have increased will WBC have the courage to admit 20s Plenty is not working and remove these 20 areas?