West Sussex Fire and Rescue Service said just after 4.30am that it was on scene at a road traffic collision on the A23 between Martyrs Avenue and the Tushmore roundabout.
The crew and Heavy Rescue Tender from Crawley Fire Station supported police officers at the scene.
The fire service said there was a road closure in place 'so please allow extra time for your journey'.
Sussex Police said the road would be closed 'for some time' after the collision on London Road, at the junction with Manor Royal.
According to traffic reports, the road remains closed southbound, as of 8am,
'Severe delays' have been reported on A2011 Crawley Avenue eastbound.