The A27 Shoreham Bypass was closed for over seven hours this morning after two cars were involved in a serious accident.
The crash happened near the Shoreham Airport traffic lights at the Sussex Pad.
The road was closed between the Lancing Manor roundabout and the Shoreham flyover from 5.30am until about 12.30pm.
Police say an 11-year-old boy was among those "seriously" injured in the crash.
It involved a red Peugeot and a white Vauxhall Vivaro van which collided at the crossroads.
Inside the Peugeot a 50-year-old woman and an 11-year-old boy suffered serious injuries, while a 39-year-old van driver suffered minor injuries.
The fire service confirmed that two casualties had to be cut free from the wreckage of one of the vehicles.
Police say the eastbound carriageway is likely to stay closed until at least 11am while an investigation is completed and the scene cleared.
Officers have launched Operation Fairmile, and have appealed for any witnesses or anyone with dashboard camera footage to come forward.
The westbound carriageway is being reopened.
The accident happened on the eastbound side.
The westbound carriageway was closed to allow the air ambulance to land.
Follow the latest live updates here.
Two casualties were cut free from the wreckage and taken to hospital.
Part of the #A27 is currently closed following a two-vehicle crash at the junction with Coombes Road, #Shoreham.
— Sussex Roads Police (@SussexRoadsPol) November 19, 2018
Westbound traffic is moving slowly, however the eastbound carriageway is likely to be closed until at least 11am.
Please plan ahead and avoid the area if possible.
Fire crews have left the scene, but said the road will "remain closed for some time" while police investigate.
Follow the latest live updates here.
Sgt Richard Hobbs from the Roads Policing Unit Tweeted to say the westbound carriageway had reopened at 7.23am.
There is no estimate for how long the eastbound carriageway will remain closed but the westbound carriageway has now re-opened.
Follow the latest live updates here.
A fire service spokesman said crews from Shoreham and Worthing attended the "nasty" crash scene.
⚠️ Crews have been dealing with an RTC on the #A27 between #Lancing & #Shoreham this morning. Both east & westbound carriageways affected with eastbound likely to be closed for some time. Photo credit: Eddie Mitchell @brightonsnapper pic.twitter.com/HE2ofqhuZP
— West Sussex Fire & Rescue Service (@WestSussexFire) November 19, 2018
Traffic from Worthing to Brighton is affected.
Sussex Police said in a statement: "Police are currently at the scene of a two-vehicle collision on the A27 at Shoreham.
"A white Vauxhall Vivaro and a red Peugeot 308 collided at the crossroads with Coombes Road shortly before 5.30am on Monday (19 November).
"The Peugeot driver – a 50-year-old woman – and her passenger – an 11-year-old boy – have both been taken to Royal Sussex County Hospital in Brighton with serious injuries.
"The Vauxhall driver – a 39-year-old man – has been taken to the same hospital with minor injuries.
"The eastbound carriageway is likely to remain closed until at least 11am for investigations and recovery to take place, and local diversions are in place.
"One lane of the westbound carriageway is open at this stage.
"Police are appealing for witnesses or anyone with dash cam footage of the incident to report it online or call 101, quoting Operation Fairmile."
Follow the latest live updates here.
#A27 Update. #Sussex @SussexRoadsPol have extended the closure in both directions. It is now between the #A293 #Hangleton and the #A2025 #Lancing due to a serious road traffic collision.Emergency Services working at scene.
— Highways England (@HighwaysSEAST) November 19, 2018
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