The easiest way would depend on your mode of transport and time of day. At a good time of the day, it would be quite easy to jump on the freeway by heading to the South St or Leach Hwy on-ramps. If you were closer to the Canning Hwy side of Melville, then you could drive to the Canning Hwy freeway entry and try that route. Otherwise, there are buses and/or the nearby train station on Leach Hwy. These may be a more cost effective option if you can walk there and obviously you save on parking in the city. The tiem difference might be 30 mins for car and 15 for train, or at a good time of day the car could be just as quick. You'd have to factor in any time lost or gained by walking to your ultimate destination eg: office.