Greensborough Highway Patrol intercepted a vehicle in Thomastown following reports of an erratic driver travelling north near Wollert this morning.
Numerous calls to Triple 0 (000) were received after the Toyota Rav 4 was seen on the Hume Freeway about 4.20am.
Police located the vehicle in Thomastown and the 44-year-old woman from Casey in the ACT returned a positive evidentiary breath test of .144.
Her vehicle was impounded for 30 days and her licence was immediately suspended.
The woman is expected to be charged on summons with drink driving, drive in a manner dangerous and other traffic related offences.