(Portland, OR)  --  A woman who was flagging traffic in a construction zone in Southeast Portland is in critical condition after being hit by a car.  Police say Margot Davis was standing on a sidewalk in the area of Southeast Division Street and 68th Avenue when she was hit yesterday afternoon.  Authorities say the 49-year-old driver of the car had been inhaling nitrous oxide prior to the crash and has been arrested.  His name hasn't been released.