The number of bridges unable to carry the heaviest vehicles on Britain’s roads has risen for the second year running, new figures show.
Local authorities identified 3,211 bridges as being substandard at the end of last year, the RAC Foundation said.
That is up 3.4% on the total of 3,105 in 2020, and up 5.1% on the figure of 3,055 in 2019.
Many of these bridges are subject to weight restrictions, while others are under programmes of increased monitoring or even managed decline.
Cracks in the pedestals of Hammersmith Bridge, west London, have led to motor vehicles being banned from using the 135-year-old cast iron structure since April 2019.
Councils reported that 17 bridges fully collapsed during the previous 12 months.
Twelve were in Dorset and five were in Denbighshire.
A further 37 had partially collapsed.
Many of these were relatively short structures.
Devon has the highest number of substandard bridges at 229, followed by Oxfordshire (222), Essex (167), Somerset (128) and Cornwall (124).
Some are substandard because they were built to earlier design standards, while others have deteriorated through age and use.
Between them, local authorities say they would ideally want to bring 2,374 of the 3,105 substandard bridges back up to full carrying capacity.
But budget constraints mean they anticipate that only 379 will have the necessary work carried out on them within the next five years.
The analysis was based on data provided by 196 councils in response to freedom of information requests, and was carried out in partnership with Adept, a group representing local authority bosses responsible for transport and other sectors.
RAC Foundation director Steve Gooding said: “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.
“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.”