The video viewer to the left will show you a a few very brief excerpts from  Running Trains.  This is just a low-resolution sample, suitable for the Internet, remember.  The DVD is professional quality. 
This preview is in Windows Media format and will probably play without problems if you have a PC.  If you have a Mac with Quicktime, you may need a simple plug-in to watch this kind of file.  You can download this plugin at Flip4Mac