A woman and an 11-year-old boy were taken to hospital with serious injuries following a crash on the A27 in Shoreham.
A white Vauxhall Vivaro and a red Peugeot 308 collided at the crossroads with Coombes Road shortly before 5.30 on Monday morning.
The Peugeot driver – a 50-year-old woman – and her passenger – an 11-year-old boy – were both taken to Royal Sussex County Hospital in Brighton.
The Vauxhall driver – a 39-year-old man – was taken to the same hospital with minor injuries.
The eastbound carriageway was closed until about midday while investigations and recovery were carried out but has since reopened.