Investigators are currently still on the scene between Pulborough and Billingshurst.
Emergency services were called to the area at 21.41pm last night.
Crash investigation work is ongoing today at Stane Street between Black Gate Lane/Broomers Hill Lane and the B2133 Adversane Lane.
Brinsbury College earlier advised students heading to the college for a GCSE maths exam today to allow extra time for their journey.
A spokesperson said the road was now open from the Pulborough direction but there were traffic delays in the area.
“If you are travelling from the Horsham/Crawley/Billingshurst area, there will be diversions and delays.”