Alan, Mary, and Robert on a train, possibly Canadian Northern.  From the Robert McKay Brebner fonds, Provincial Archives of Alberta, PR2009.0499/314. (Circa 1905 per the flickr captions/discussion. Not Canadian National as the children would have been adults circa 1918).
<a rel="nofollow" class="external text" href="https://www.flickr.com/people/95711690@N03">Provincial Archives of Alberta</a>
<a rel="nofollow" class="external text" href="https://www.flickr.com/photos/alberta_archives/29215867126/">Brebner children on a train</a>