Rail electrification disruption in St Brides Wentlooge
Disruption in south Wales caused by work to bridges ahead of major work electrifying the railway line has begun with a 10-mile road diversion.
Network Rail says bridges will need to be raised for electrical cables from London to Swansea and the valleys.
A diversion lasting six months has begun at St Brides Wentlooge, Newport.
The company says it hopes to keep disruption to a minimum, but a local pub says lack of passing trade means it could close in weeks.
Network Rail said bridges along the rail route would need to be modified, with its project management team still surveying which ones would be affected.
A spokesman said bridges would either be raised or the railway line dropped, although this was not the preferred option because of the risk of flooding.
The company, which is responsible for the UK's railway network, said it aimed to have as little diversion of traffic and other disruption as possible.
But residents and businesses in St Brides Wentlooge are concerned that the work in their village is scheduled to last for half a year.
Sue Jones, landlady at the Inn at the Elm Tree, said business was "zilch" since the bridge closed on Monday.
"We get a lot of passing trade as we are a hotel and restaurant, as well as a pub," she said.
"But we aren't getting that now as the bridge was the main route from Newport. Who's going to drive an extra 10 miles to the pub?
"The way it's going we'll be lucky to still be open at Christmas. It's scary."
The Pheasants bridge, which carries the B4239 Lighthouse Road over the railway, means a journey from St Brides Wentlooge to Duffryn in Newport is usually two miles.
The bridge closure means traffic has to travel through nearby Marshfield and along the A48 dual carriageway to Duffryn and on to Newport city centre.
Cathy Turner, clerk of the local community council, said: "It's not very good at all and I know businesses are worried.
"We understand the work needs to be done but surely it can be done quicker than six months.
"We are worried that another bridge in Marshfield will be the next to be closed and that will cause more problems," she added.
Network Rail said the work in the area was essential and the diversion route was the only option available.
"To minimise the potential disruption faced by the local community, Network Rail is paying for an additional bus to supplement the bus service between Newport and St Brides," a spokesperson added.
"This additional bus service should allow residents to continue receiving the service they are used to throughout the road closure."
Network Rail is also meeting the costs of the work on the bridges, rather than local councils.
The Department of Transport announced earlier this year that the Great Western rail line between London and Swansea will be electrified, along with commuter lines in the south Wales valleys.
Extending the electrification of the main rail line will cut some 20 minutes from the three-hour journey between Paddington and Swansea.
It also means newer, longer trains will be able to run on the line, powered by overhead cables.