01-11-2016, 01:09 PM
Because that's are how modern railroad signaling works. Railroad use multiple signal heads to convey many indications to train crews, more than just stop, slow, and go.
This is a basic overview: <!-- m --><a class="postlink" href="http://www.viarail.ca/en/about-via-rail/capital-investment/article/light-show">http://www.viarail.ca/en/about-via-rail ... light-show</a><!-- m -->. However, you should know that most railroads have developed their own systems, so a certain aspect on CN could be something different on BNSF or CSX.
This is a basic overview: <!-- m --><a class="postlink" href="http://www.viarail.ca/en/about-via-rail/capital-investment/article/light-show">http://www.viarail.ca/en/about-via-rail ... light-show</a><!-- m -->. However, you should know that most railroads have developed their own systems, so a certain aspect on CN could be something different on BNSF or CSX.