Motorists are being advised to prepare for delays while a 231-tonne lorry passes slowly through Gloucestershire.

National Grid will transport a new piece of vital equipment to Iron Acton substation, South Gloucestershire, on Sunday, 30 July.

A transformer, a piece of equipment that reduces high voltage electricity down to lower voltage used on regional networks, will begin its journey from Avonmouth Port in Bristol, at 9am.

A special, heavy haulage lorry will transport the transformer. The lorry will be 57 metres long by five metres wide and weigh 231 tonnes.

Due to the size and weight, the lorry will travel between 10 and 15 miles per hour.

A police escort and special haulage team will accompany the lorry to ensure the safety of the public and the transport team.

The police escort will also be there to manage traffic and to halt traffic for a short time at certain places, such as when the lorry needs to straddle two road lanes, turn or travel along narrow roads.

Due to the size of the lorry, it must take an indirect route to Iron Acton substation to avoid hazards, such as weak bridges and narrow turning points.

The lorry will leave Avonmouth docks via the M49. It will then head east on the M4 before joining the M5 northbound. The lorry then travels to Junction 13 before returning southbound, where it will exit onto the B4509 at Junction 14.

Finally, the lorry passes through the villages of Cromhall, Bagstone and Rangeworthy, and then follows the B4059 until it reaches Latteridge village, close to its final destination in the afternoon.

National Grid project engineer Paul Taunton, said: "We've worked closely with Allelys Heavy Haulage Ltd to plan a safe delivery route and to keep disruption to a minimum.

"But there are likely to be some delays on the Sunday morning on the motorway and on smaller, narrow roads close to the substation.

"I'd like to thank everyone for their patience in advance of our work. By letting people know in good time, we hope that drivers will be able to plan their route on the 30 July to avoid any disruption.

"Our last delivery to Iron Acton substation was successfully carried out with very little disruption and we expect the same this time.

"If anyone has questions or concerns, they can contact our Community Relations team on 0800 073 1047. They are available seven seven days a week from 7am to 7pm."