Cornwall's motorists will have 21 road closures to avoid nearby on the National Highways network this week.

And one of them is expected to cause moderate delays – with drivers facing a wait of between 10 minutes and half an hour.

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

• A30, from 8pm April 5 to 6am May 6, slight delays (under 10 minutes): A30 between Chiverton Cross and Carland Cross traffic signals for Chiverton to Carland improvement scheme.

• A30, from midnight, April 2 to 11pm October 8, slight delays (under 10 minutes): A30 St Erth used by GWR Railway Replacement Buses on St Erth to St Ives route.

• A30, from 8pm June 30 2021 to 6am December 1 2023, slight delays (under 10 minutes): A30 Zelah narrow lanes and 50 mph speed limit for Chiverton to Carland improvement scheme.

• A30, from midnight, September 1 2020 to 6am December 16 2023, slight delays (under 10 minutes): A30 Carland Cross to Chiverton Cross improvement scheme.

And a further 17 closures will begin over the next seven days:

• A30, from 7.30pm May 2 to 6am May 4, slight delays (under 10 minutes): A30 both directions St Erth Roundabout to Loggans Moor Roundabout closed for general maintenance works. Diversion via B3301 through Hayle.

• A30, from 8pm May 2 to 4am May 3, slight delays (under 10 minutes): A30 both directions Innis Downs to Victoria - lane closure for barrier/fence safety repairs.

• A38, from 8pm May 2 to 6am May 3, slight delays (under 10 minutes): A38 Tideford to Landrake traffic signals and convoy working for road markings.

• A30, from 9pm May 2 to 6am May 3, slight delays (under 10 minutes): A30 eastbound, Twobridges - lane closure for electrical works.

• A30, from 10pm May 2 to 6am May 3, slight delays (under 10 minutes): A30 both directions Colliford Lake lane closures for barrier repairs.

• A38, from 8pm May 3 to 6am May 4, slight delays (under 10 minutes): A38 both directions Carkeel lane closures, traffic signals and convoy working for road markings.

• A30, from 8pm May 4 to 4am May 5, slight delays (under 10 minutes): A30 both directions Highgate Hill to Victoria - lane closure for barrier/fence safety repairs.

• A30, from 8pm May 5 to 4am May 6, slight delays (under 10 minutes): A30 eastbound, Callywith - lane closure for barrier/fence safety repairs.

• A30, from 7pm May 9 to 6am May 11, slight delays (under 10 minutes): A30 eastbound, Bolventor to Fivelanes lane convoy working for resurfacing.

• A30, from 7.30pm May 9 to 6am May 12, slight delays (under 10 minutes): A30 both directions Loggans Moor to Treswithian closed for general maintenance works. Diversion via minor road through Roseworthy and Connor Downs.

• A30, from 8pm May 9 to 6am May 10, moderate delays (10-30 minutes): A30 eastbound, Bolventor exit and entry slip road closures for resurfacing, exit slip diversion via A30 eastbound to Fivelanes and return, entry slip diversion via A30 westbound to Temple.

• A38, from 8.30pm May 9 to 6am May 31, slight delays (under 10 minutes): A38 both directions Dobwalls to Turfdown near Bodmin, carriageway closures for resurfacing, diversion via A390, B3269, B3268 and Turfdown Road.

• A30, from 7pm May 10 to 6am May 11, slight delays (under 10 minutes): A30 westbound, Mitchell lane closure for Instalcom.

• A30, from 7pm May 15 to 6am May 19, slight delays (under 10 minutes): A30 both directions Scorrier to Boxheater (B3285) carriageway closures for improvement scheme, eastbound, diversion via Blackwater, A3075 and B3285, westbound, diversion via B3285, A3075, Blackwater and A3047 to Avers junction.

• A30, from 7pm May 15 to 6am May 20, slight delays (under 10 minutes): A30 eastbound, Pennygillam junction, Launceston, exit slip road closure for Cornwall Council works, diversion via A30 to Tavistock Road junction.

• A30, from 7.30pm May 15 to 6am May 17, slight delays (under 10 minutes): A30 both directions Longrock Bypass carriageway closures for maintenance works, diversion via Longrock.

• A38, from 8pm May 15 to 5am May 16, slight delays (under 10 minutes): A38 both directions Tideford to Kilner Quay. 2-way signals for drainage work.

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