SA man falls asleep at wheel of Porsche

A man has been charged with drink driving after police found him asleep at the wheel of his Porsche at a green light in Adelaide.

The 43-year-old was woken when police knocked on the window of the luxury car in the early hours of Wednesday morning in Adelaide's CBD.

Once he was woken the man quickly sped off and officers gave chase eventually boxing him in at a nearby street, police say.

The man recorded a blood-alcohol reading of 0.114, and will appear in Adelaide Magistrates Court on November 25 charged with drink driving and engaging in a police chase.