The Forest of Dean's motorists will have 12 road closures to avoid nearby on the National Highways network this week.

And one of them is expected to cause severe delays – with drivers facing a wait of at least 30 minutes. Another five will cause moderate delays of between 10 minutes and half an hour.

The latest expected works list, with notes from National Highways, shows that two closures already in place are expected to carry on this week:

• A40, from 9.38am November 30 to 4pm December 4, slight delays (under 10 minutes): A40 Lea to Huntley traffic lights in place for Severn Trent Water works.

• A40, from 9am November 27 to 4pm December 15, slight delays (under 10 minutes): A40 both directions Huntley. 2-way signals for private residence boundary wall repair.

And a further 10 closures will begin over the next two weeks:

• M48, from 7pm December 4 to 6am December 6, moderate delays (10-30 minutes): M48 eastbound, junction 2 to 1 Severn Bridge - carriageway closure for structure maintenance. Diversion via M4 Prince of Wales Bridge.

• M48, from 7pm December 4 to 6am December 6, slight delays (under 10 minutes): M48 westbound, junction 1 to 2 Severn Bridge lane closure for structure maintenance works.

• M50, from 9pm December 4 to 6am December 5, moderate delays (10-30 minutes): M50 eastbound, jct four to 2, carriageway closure for barrier safety repairs, diversion via local authority network.

• M48, from 7pm December 6 to 6am December 8, slight delays (under 10 minutes): M48 eastbound, junction 2 to 1 Severn Bridge - lane closure for structure maintenance.

• M48, from 7pm December 6 to 6am December 8, moderate delays (10-30 minutes): M48 westbound, junction 1 to 2 Severn Bridge carriageway closed for structure maintenance works. Diversion via M4 Prince of Wales Bridge.

• A40, from 9pm December 11 to 6am December 14, moderate delays (10-30 minutes): A40 eastbound and westbound, Marstow to Wilton roundabout, carriageway and lane closure due to resurfacing works, diversion via local authority Network.

• M4, from 9pm December 11 to 6am December 13, moderate delays (10-30 minutes): M4 eastbound, junction 23 to 22 Prince of Wales Bridge - carriageway closure for bridge maintenance, diversion via M48 Severn bridge.

• A40, from 10pm December 11 to 6am December 13, severe delays (more than 30 minutes): A40 eastbound and westbound, Lea to Huntley carriageway closures for maintenance, Light vehicle diversion via local road to Mitcheldean and A4316, HGV diversion via A40, A449, M50 and A417.

• M4, from 9pm December 13 to 6am December 15, slight delays (under 10 minutes): M4 eastbound, junction 23 to 22 Prince of Wales Bridge - lane closure for structure maintenance.

• M4, from 10pm December 13 to 6am December 15, slight delays (under 10 minutes): M4 westbound, junction 22 to 23 Prince of Wales Bridge - carriageway closure for structure maintenance, diversion via M48 Severn Bridge.

National Highways is responsible for maintaining motorways and major A-roads, so closures of smaller roads will not be included in their schedule.