(Portland, OR) -- Transportation officials are warning about disruptions in MAX service over the next three weeks as work continues on improving track and intersections. Upgrades on the track on Southwest Morrison and Yamhill at 11th Avenue will include removal of wooden ties, replacing track, and installing new switch machines and cables for the signal system. Officials say the improvements will help keep the MAX system moving and create a smoother ride for trains and streetcars. Shuttle buses will be operating on several streets downtown to provide alternate service for MAX and Portland Streetcar riders.