Option two. Longer traveling motorists should not use neighborhood streets to cut traffic. They will learn it doesn't buy them any time trying to use this short cut.

(I, once a week have a similar situation. I use a 25mph posted street that is a designated bicycle route, heavily used by cyclists, speed humps with 20mph posted. I take the lane and ride 20-25mph. The only way motorists find this back way faster than the parallel arterials is if they speed at 35mph, which is inappropriate on this road. They can travel at 20mph behind me. When I occassionally motor this same route (as it leads to my home, not as a short cut) I also drive 25mph and lines of want to be speeders pile up behind me - if they are in such a hurry they should take the 45mph arterial)

Or modified option one which is to filter to the left of the line of cars, if this is possible.

Al