Police are appealing for witnesses to a fatal collision on Street End Road in Sidlesham at 7.10am on Friday (September 28).
A red Alfa Romeo was in collision with the trailer of a tractor being towed in the oposite direction.
The tractor was carrying bales of straw which fell onto the car.
Sargeant Carl Knapp said: “Sadly, the 70-year-old man from Portsmouth, who was the only occupant of the car, has died following the collision.
“The driver of the tractor, a 25-year-old man from Chichester, has been arrested on suspicion of death by careless or dangerous driving.”
Two other cars were involved but no-one else was injured.
Anyone who has information is asked to contact police quoting Op Dovecot.