The data is included in the council's highways 'asset performance report' for 23/24, published in advance of a meeting of the council's highways and transport cabinet panel.

It shows that 'maintenance should be considered' on 18 per cent of the county's 3244km of 'U' or 'unclassified' roads – up from 10 per cent in the previous year (22/23).

And it puts the increase down the impact of extreme weather, combined with the underlying condition of the 'U' roads.

According to the data, the percentage of the county's 'U' roads that should be considered for maintenance is higher than in any of the past eight years.

And the 18 per cent figure is reported to be one per cent above the national average of 17 per cent.

Between 2017/18 and 2021/22 the council did commit an additional £29m to improve the county's unclassified network.

And that was with the ambition of halving the percentage of roads that should be considered for maintenance – from the 16 per cent in 2016/17 to eight per cent.

But after dropping as low as seven per cent in 19/20 and in 21/22, the percentage of 'U' roads that should be considered for maintenance increased to 10 per cent in 22/23 and to 18 per cent in 23/24.

Accounting for the increase the report suggests the number of roads requiring 'treatment' in 23/24 was due to the impact of the weather and the underlying conditions of the roads.

"Extreme heat, cold, precipitation has significantly damaged the unclassified road network," says the report.

"Much of the unclassified road network is referred to as "evolved" where it could have been a historic track that has been made up over a number of years, rather than being a "designed" road.

"The foundations of undesigned roads are much more susceptible to damage if moisture is allowed to penetrate through the surface."

Meanwhile, according to the report, the proportion of 'A' roads in Hertfordshire that the report considered to be in need of maintenance is just three per cent – one per cent lower than the England national average.

And the proportion of 'B' and 'C' roads in the county where maintenance should be considered is four per cent – compared to a national average of seven.

According to the report, the condition figures for 'A', 'B' and 'C' roads are "more stable and accurate" as they are taken from machine surveys of the road surface.

But, it says, the figures for U roads are "more sensitive" because they are based on "a more subjective" visual inspection.

In the report officers report that they are looking at dropping the visual inspections, in favour or a survey that would use artificial intelligence technology, "once we are confident that the AI technology provides consistent and reliable information".

Overall, according to the report, the county has a network of 5100km of roads.

Of those 325km are 'A' road dual carriageways, and 371 single carriageway 'A' roads.

A further 332km are classed as 'B' roads and 826km as 'C' roads. More than half of the county's road network – 3244km – is classed as unclassified or 'U' roads

According to the report the county council is responsible for 32.5m sq m of carriageway – equivalent to 4500 football pitches. And it has a current value of around £6.5billion.

Meanwhile the council 5632 km of footways and 144km of dedicated cycle ways.