A Montana Rail Link helper set curves into Austin, Montana, on June 29, 2016, heading back to Helena to help another train up Mullan Pass. Note how No. 4302, the eastern locomotive in the consist is the most filthy—this is due to being the last unit into Mullan Tunnel, and getting the most exhaust and dirt from the lead locomotives. MRL really does try to keep their locomotives clean, but helper service up the demanding 2.2 percent mountain grade of Mullan takes its toll on cleanliness quickly.
