Police cameras used to detect speeding drivers will continue to be set at 30mph even if Holyrood passes legislation to cut the limit in built-up areas to a default 20mph, MSPs have been told.

Police Scotland Chief Superintendent Stewart Carle said if a bill to reduce the speed limit in residential roads is approved, officers would enforce it.

But, he insisted 20mph zones will "not be a priority" because the majority of casualties occur on faster roads.

Chief Supt Carle, divisional commander in the force's road policing unit, told the Rural Economy and Connectivity Committee: "Our safety camera units, meantime, their equipment is not calibrated for 20mph so they will continue to be deployed on 30 and above, so you won't expect to see them suddenly switching into urban areas."

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Green MSP Mark Ruskell wants to change the law to reduce the speed limit in residential streets and built-up areas, and has introduced a Member's Bill at Holyrood.

But Transport Secretary Michael Matheson said there are a number of "challenges" with the Restricted Roads (20mph Speed Limit) (Scotland) Bill.

The Scottish Government supports 20mph zones "where there is a good evidence base for them to be introduced".

The bill would cut the limit on restricted roads - those with street lighting which are not classed as either A or B roads.

Mr Matheson said: "We don't know the numbers of restricted roads in Scotland, there are some restricted roads actually you wouldn't want to have as 20mph zones, there are roads which are not restricted you would possibly want to have as 20mph roads as well.

"This is a Bill that is intended to apply not to a town or a city, but to a country. And we are in a situation where our local authorities don't have the information around restricted roads.

"There are thousands of restricted roads in Scotland, but because most of it was done on paperwork over many, many decades, it would be a massive undertaking for local authorities to go through in order to collate all that information and identify that information."

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He also insisted it is not known how much it would cost to introduce the legislation - suggesting the indicated financial impact on councils of £21 million to £22 million could be an underestimate of the true figure.

The Transport Secretary was also clear there is no funding in his budget to meet the cost of the change.

He told the committee: "Any financial support we would have to give to local authorities - and I recognise we would have to give them financial support to assist them with this matter - would have to come out of existing budget allocations."

Speaking after the committee meeting, Mr Ruskell said: "The evidence is clear: introducing a 20mph limit in residential areas across Scotland would save lives.

"The Scottish Government must now back my Bill if it's serious about saving children's lives."

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