Sussex Roads Police said a vehicle was stopped on the M23 and the driver failed a DrugWipe test.
Cocaine and cannabis was found in the vehicle, police said.
The driver was arrested on suspicion of drug-driving and being in possession of Class A and B controlled drugs.
The police spokesperson said: "Driver faces a disqualification from driving if the results come back over."
Sussex Police Chief Constable Jo Shiner issued a statement following this arrest.
A Twitter post read: "Sussex Police will continue to be very proactive on our roads to tackle drink and drug driving.
"It costs lives, and causes misery for the victims families and loved ones. If you see it or suspect it then please report it #drinkdrugdrivingcostslives."
Have you read?: Dial 999 if you see this man in Horsham or Crawley