A driving instructor was arrested after he provided a positive drug test while supervising a learner, police said.
Suffolk Police said the 30-year-old was stopped on Lindbergh Road, Ipswich, on Thursday, and tested positive for cocaine after a roadside "drug wipe".
He was arrested on suspicion of drug-driving and taken to police headquarters where a blood sample was taken for further testing.
Police said he has been released under investigation pending the test results.
A drug wipe is where a swab is taken from the suspect's mouth, providing an instant reading.