Maintenance spending on motorways and major A roads in England fell by 39% during the first seven years of this decade, and came down by 13% on local authority roads.

Over £1.4Bn was spent on maintenance in 2009/10 on strategic routes, falling to £896M in 2016/17. Spending on local authority roads fell from nearly £4.2Bn a year to £3.6Bn over the same period.

Skidding resistance on principal local authority roads in England appears to have deteriorated, with 27% of roads surveyed requiring further investigation around the middle of the decade, up from 23% earlier in the decade.

On motorways, the percentage of lane one length requiring further investigation for the purposes of skidding resistance has increased over 10 years, from 1% in 2007/08 to 5% in 2016/17, but the figure fell from 10% in 2015/16.

For trunk A roads, the percentage requiring more study for skid resistance increased from 11% to 19% between 2007 and 2017, but again saw a welcome fall from 26% in 2015/16.

On a positive note, the surface condition of motorways in England has improved, with the percentage of lane one length requiring further investigation falling from 6% to 2% over the last 10 years. But the surface condition of trunk A roads requiring further investigation has remained broadly stable at between 4 and 5%.

The Association of Directors of Environment, Economy, Planning & Transport's engineering board chair Mark Stevens said the latest road condition statistics provide evidence of a "downward spiral" in highway condition.

"As our road surfaces continue to wear away, skid resistance inevitably diminishes, so the task of keeping local roads ‘safe’ becomes ever more daunting. Even if central Government was to double its current £1.2Bn annual investment in local roads, it would still take a decade to clear the road maintenance backlog, but that has to be regarded as the minimum level of extra investment that should be made to stop the country’s road network from getting to an unsalvageable position."

He added that local highway authorities continue to be under immense pressure to maintain their road networks in a safe condition. "However, with growing financial pressures for adult social care and looked-after children in conjunction with an ongoing squeeze on overall local government finance, highway maintenance remains the poor relation."

Following the report, the Road Surface Treatments Association called for the greater use of high friction surfacing and other surface treatments to improve skid resistance.

It also warned that deterioration in skid resistance could be an early indicator that the road as a whole needs intervention.

RSTA chief executive Mike Harper said: “The deterioration of safety levels on our roads is alarming and is the direct result of the lack the investment in road maintenance. In addition to the possible threat of loss of life, reduced skid resistance can be expensive as the associated accident and investigation costs of non-motorway fatal accidents are calculated to be £1.4 million per fatal accident.”

He added: “With highway budgets under pressure, in most cases skid resistance can be restored without major resurfacing works.”