NO ONE disputes the chances of killing or seriously injuring a child at 20mph are many times lower than at 30.

Nor do they question that Lancashire’s new 20mph limits have cut accidents or that the drop Blackburn with Darwen’s drop in young road accident victims stalled after it slowed its programme of introducing of low speed residential zones.

The argument is whether the cost – up to £9 million in the county council area and upwards of £500,000 in the borough – of covering residential areas with 20mph residential speed limits instead of small zones dotted around makes a big enough difference.

In the Lancashire police force area the number of children killed and seriously injured dropped from 152 in 2006/7 to 83 in 2012/2013 with Burnley, Hyndburn, Rossendale and Pendle all recording significant drops.

The South-West Burnley pilot area, one of the first parts of Lancashire’s 20mph speed limit roll out, saw the number of child casualties fall from 31 injuries and two serious casualties in three years to five and none over 15 months.

A study for the Department of Transport concluded that in Portsmouth (the first major town to have a total 20mph residential speed limit) road casualties fell by 22 per cent compared to 14 per cent nationally in the two years after introduction in 2008.

Blackburn with Darwen has 21.7 per cent of the population under 16, one of the highest proportions in the UK.

In 2006 it had 13 serious injuries and two deaths – three-year-old Demi-Leigh Hitchen and seven-year-old Olivia Whiteside.

The British Medical Journal concluded in 2009 that 20mph zones in London halved the number of child road accident casualties.

In the Netherlands a campaign of introducing 30kph (18.6mph) residential speed limits saw accidents drop by more than 80 per cent and injuries by more than 60. Following good results in Austria, the European Commission encouraging 30kph residential speed limits in all major EU towns and cities.

In the USA, home of the car culture, 46 out of its 55 states and self-governing territories have residential speed limits of 25mph or lower including one where all streets are 15mph and some as low as 10mph.