Drivers in and around the Forest of Dean will have 10 National Highways road closures to watch out for this week.

And one of them is expected to cause major delays – with motorists facing a wait of at least 30 minutes. Another two 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 7pm July 17 to 7am July 30, slight delays (under 10 minutes): A40 Over to Lea used as a diversion route for Gloucestershire County Council closure of the A449 Preston Cross.

• A38, from 8pm January 8 to 6am August 3, severe delays (more than 30 minutes): M5 northbound and southbound, junction 7 to junction 9, M50 eastbound, and westbound, junction 2 to M5, carriageway, slip road, lane closures, with 24/7 narrow lanes, lane closure, and 50mph speed limit due to improvement works, diversion via National Highways and local authority network.

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

• A38, from 9am July 22 to 6pm August 8, slight delays (under 10 minutes): M50 both directions M5 jct eight to A449 Travellers rest roundabout, Lane closures for maintenance works.

• A40, from 7pm July 22 to 6am July 25, slight delays (under 10 minutes): A40 Huntley, traffic lights installed by Gigaclear.

• M4, from 8pm July 23 to 6am July 26, moderate delays (10-30 minutes): M4 eastbound, junction 23 to 22 Prince of Wales Bridge closed for carriageway renewals, diversion via M48 eastbound to M4, junction 21.

• M5, from 9pm July 23 to 6am July 24, slight delays (under 10 minutes): M5 northbound, junction 12, lane closure for electrical works.

• M4, from 8pm July 27 to 6am July 28, moderate delays (10-30 minutes): M4 westbound, junction 21 to 23 closed for carriageway renewals, diversion via M48 westbound. M49 northbound, traffic via M4 east to M5, junction 16, u-turn, M5 northbound to junction 15 and M4 westbound.

• M50, from 9pm August 1 to 6am August 2, slight delays (under 10 minutes): M50 westbound, junction 1 to junction 2, Lane closure for maintenance.

• M5, from 10pm August 1 to 6am August 2, slight delays (under 10 minutes): M5 southbound, junction 13 to 14, lane closure for barrier repairs.

• M50, from 9pm August 4 to 6am August 5, slight delays (under 10 minutes): M50 eastbound, junction 2 to junction 1, Lane closure for maintenance works.

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