Police are at the scene of a two-vehicle collision on the A27 at Shoreham which saw a woman and a child taken to hospital with serious injuries.
A white Vauxhall Vivaro and a red Peugeot 308 collided at the crossroads with Coombes Road shortly before 5.30am this morning.
A 50-year-old woman and her passenger, an 11-year-old boy have both been taken to Royal Sussex County Hospital Brighton with serious 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.