The structure of this site has been kept very simple, giving a priority to pictures. In every page there is a title, some text, some pictures and a return or progression icon. The active text is blue, other links are:
photo enlargement: all small pictures can be enlarged, click over them. With some browsers, and depending on your settings, the picture is surrounded by a colour line and the text "Click to enlarge" appears when the mouse is over the picture;
enlarged pictures, return to the original page: a small icon representing the picture, can be accompanied by a small icon representing the next picture in a series;
next page: a blue double arrow » ;
return to the home page or, for the rolling stock, to the list: a small icon representing a locomotive 
;
The title of a series of pages including some new items is accompanied by a blinking star.
An active text in grey indicates that the text is not the definitive one, or is being translated, or that the linked pages are being modified.
And now, good navigation, although the word "navigate" can appear incongruous in a site dedicated to a railway.