A Chichester man was arrested on suspicion of driving whilst unfit through drugs after a report of erratic driving on Tuesday, according to Sussex Police.
Police said officers followed a car after receiving reports that it had been 'staggering around a car park' in Midhurst before driving off in an 'erratic manner'.
A spokesman said: "A member of the public called police at 10.11pm having seen the man in the car park at Cocking Hill before driving off towards Singleton.
"His car was spotted a short time later and was stopped at Oving where he was arrested.
"A 31-year-old man from Chichester was arrested on suspicion of driving a vehicle whilst unfit through drugs and attempting to possess a controlled drug of Class B - ketamine. He was later released under investigation."