Over half of London’s bridges across the River Thames are in ‘poor’ or ‘very poor’ condition, the worst possible ratings, with the crossing in Chelsea deteriorating after heavy vehicles were recently diverted from a nearby crossing.

Just six of the 30 bridges that supplied data are in good or fair condition, said Satbir Gill, chairman of the London Technical Advisors Group, a local government advisory body. Eight have yet to supply the requested detail, he told the transportation committee of the London Assembly on Tuesday, with full details expected to be published next month.

Ageing infrastructure and extreme weather have hit the UK’s river crossings, with Hammersmith Bridge shut to traffic for more than seven years and Waterloo Bridge is heading toward closure within three to four years unless vital repairs are carried out.

Bridge are rated by the specific authority or organization that owns and maintains them. Poor ratings can lead to precautionary weight limits, lane closures, or restrictions on heavy vehicles such as buses crossing the structures.

The increased traffic flowing over Chelsea Bridge means an interim assessment will be needed to see “if there is any increase in the rate of the deterioration of the bridge,” Andrew Burton, director of highway and regulatory services at the Royal Borough of Kensington and Chelsea, told the hearing.

Adding to the potential problems, London Bridge is undergoing an earlier-than planned engineering review, Bloomberg News reported, following a bridge collapse that happened in Germany two years ago. Structural reviews are also planned for Blackfriars Bridge, Southwark Bridge and Tower Bridge, the City Bridge Foundation said last week.