Southern SD45 at Nemo

[Batman]

another Nemo tunnel view i have found.

[Michael Knight]

Cool shot!

[NSyorktown]

Nice photo! 

It is interesting, as the tunnel face looks pretty clean in this view.  More recent pics of that same portal have a lot of soot built-up right above the entrance.  That either means today's diesels burn "dirtier" or that this photo was taken after a storm (when the rain cleared off the southern exposure into the mountain).  My guess is the traffic is heavier these days, and more powerful locomotives means more smoke.

RDS