A learner driver has been caught speeding 40km/h over the limit while his supervisor has returned a blood alcohol reading almost five times the legal limit.

Police booked the 17 year old for speeding after he was caught driving at 120km/h in an 80km/h zone on Bald Hills Rd on Sunday.

Police say his driver, who was the qualified supervising licence-holder in the car, was breath tested and returned .248%.