A taxi driver was slashed after picking up a passenger.
Police said the driver, 44, picked the suspect up in Dewsbury Moor and dropped him off in Cleckheaton at around 6pm yesterday.
The driver was cut on the hand when the suspect pulled out a knife before getting out of the car on Whitcliffe Road.
The suspect dropped the knife and a mobile phone after leaving the car.
Police are questioning a 19-year-old man in connection with the incident.
He remains in custody and police said enquiries are ongoing.