That's exactly what it is. I think its main purpose is to supply the air conditioning in the train.
discover uploadDec 20, 2013
regional train to Rognan leavin Bodø
daytrain to Trondheim leaving Bodø
train from St Ives entering St Erth station
topbound train arriving in Ringlikon station
eastbound train to London near Penzance
International "Regional" service from Narvik to Luleå
International service from Ventimiglia to Cuneo
"Rheintalexpress" between Sargans and Trübbach
Regiontog 602 (Bergen-Oslo S) between Finse and Haugastøl
discover uploadJan 1, 2012
local train in the hills of Appenzell near Gonten
discover uploadJan 1, 2012
Subwaytrain near the Hamburg harbour
EuroCity from Stuttgart zu Zurich near Singen
Train de Vignes between Corseaux and Chexbres