The number of sub-standard bridges in the UK has risen for the second year running, according to a new study by the RAC Foundation. Using Freedom of Information (FOI) requests, the organisation’s research revealed local authorities in England, Scotland and Wales identified around 3,200 bridges as being substandard at the end of 2021.

That number represents an increase of around 100 (3.4 percent) on 2020, when councils reported 3,105 bridges – defined by highway engineers as structures over 1.5m in span – as being below-par. It’s also up five percent on the 3,055 figure a year before that, but it represents a reduction compared with the 3,194 total for 2018 and the 3,441 figure for 2017.

A sub-standard bridge is defined as one that is unable to carry the heaviest vehicles seen on UK roads, including lorries of up to 44 tonnes. Many of the sub-standard bridges are subject to weight restrictions, while others will be under programmes of increased monitoring or even managed decline.

Norsworthy Bridge over the River Meavy. Burrator, Dartmoor National Park, Devon, England

And the numbers may in fact be larger, as the RAC Foundation only received responses to 196 of its 206 FOI requests – four fewer than the previous year. Between them, the 196 councils are responsible for maintaining 70,944 bridges which means around 4.5 percent of the total is substandard.

Worryingly, the figures revealed five bridges – all in Denbighshire – had collapsed, while a further 37 bridges across the UK had partially collapsed. Most of those (17) were in Denbighshire, while Conwy, Perth and Kinross, and Stirling all accounted for two partially collapsed bridges.

Car passing over a stone built bridge in Exmoor National Park England

“Bridges, as defined by highway engineers, come in all shapes and sizes, from soaring structures that span rivers and cross estuaries, through the many modest bridges designed centuries ago for the horse and cart, right down to those that are little more than culverts carrying water under a carriageway,” said the RAC Foundation’s director, Steve Gooding. “But even the failure of the shortest of these structures could mean a five-foot long gap in the carriageway, and even on relatively minor roads that can still be a headache, causing disruption and possibly a long diversion.

“What the data suggests is that councils have been fighting to hold their ground over the last five years. Whilst the increase in substandard bridges year-on-year is not huge the picture over the last five years looks more like flatlining than sustained improvement, and with the threat of more severe weather events linked to climate change that must be a worry for the overall resilience of our highway network.”