Motorists taking the A12 through Essex will have to wait until July for all the roadworks to be finished.
The maintenance on the section near Brentwood has been going on since December and was supposed to be completed last month.
But the Highways Agency says the work has been more complex than originally anticipated.
It is one of two such schemes to overrun on the road - the other, near Ipswich, is due to finish by May.
Roadworks on two stretches of the A12 are going to be around longer than planned.
Resurfacing work that started in Ipswich and Brentwood in December was due to finish at the end of this month.
The Highways Agency said weather conditions and additional works had held up progress. The improvements are now due to be completed in May.
“We found the road was in a worse state of repair than originally thought, so we have had to plane out more to compensate.
"We apologise for the delay and I’d like to thank drivers for their patience while this work continues and ask drivers to take care travelling through the roadworks and adhere to the 40mph speed limit.”
A section of the A12 around Chelmsford in Essex has been closed after a lorry overturned between Junction 17 at Great Baddow and Junction 15 for the A414. Drivers are being warned of very slow traffic.
Police in Essex have confirmed that a man in his 20s has been killed on the A12 in Essex.
The incident happened at about 3am this morning, the pedestrian was in collision with a number of vehicles.
Forensic recovery work is now taking place.
Because of that the northbound carriageway will be closed for most of the morning between the Boreham Interchange and the junction for Hatfield Peverel South.
One lane is also closed on the southbound carriageway which is also causing delays.
"This is a tragic incident where a man has died. The road will have to be closed for a number of hours during the rush hour but this is so important forensic recovery work can take place so we can find out how he died.
Motorists are asked for their patience and understanding during this time."
A man has died after becoming ill at the wheel and crashing his car in Essex.
Police were called to the A12 at Galleywood, near Chelmsford, just before 2pm on Friday.
Officers believe the driver of the car, a man in his 70s from Suffolk, became unwell and crashed into the central reservation between junctions 15 and 16.
No other vehicles were involved.
The man was treated at the scene by ambulance crews but later died.
A12 both ways closed, delays due to overturned lorry and fuel spillage at A1152 Woods Lane (Melton Roundabout). Quite a lot of fuel on the road, and the lorry on its side. Some traffic is already diverting through Melton and Woodbridge on the B1438.
One lane closed due to broken down vehicle on A12 northbound after J20a, B1137 (Hatfield Peverel South).
The A12 northbound is blocked due to an accident involving two vehicles between J20B B1137 The Street (Hatfield Peverel North) and J21 B1389 Hatfield Road (Witham South).
A12 southbound blocked due to an overturned car after J33 at the Copdock Interchange.
A lorry driver has been arrested after a crash which led to the closure of the A12 in Essex.
It happened near Marks Tey at about 1am this morning (Monday) when an articulated lorry went out of control on the southbound carriageway.
The lorry was carrying 27 tonnes of citrus fruits.
The lorry driver and passenger were taken to hospital with serious, but not life-threatening, injuries.
The driver has been arrested on suspicion of careless driving and drink or drug driving.