http://indianarailroads.org/board/index.php?topic=1795.5;wap2 <br /><br />CSX_CO:<br />The CSX &quot;Seaboard&quot; signals can be learned in 15 minutes by just about anyone. <br /><br />Bear in mind CSX uses &quot;Seaboard&quot; and &quot;Chessie&quot; signal rules on former CSX territory and former NORAC on the former Conrail.&nbsp; There are differences between the two systems and one combination of lights on &quot;Seaboard&quot; isn&#039;t the same on the C&amp;O or Conrail.<br /><br />So here goes:<br /><br />The most heads you can have on a signal is three.&nbsp; Most interlockings only have 2 headed signals, because there would be no real need for the third head.<br /><br />The top is used for your &quot;Stop, Approach, and Clear&quot; aspects.&nbsp; Bear that in mind.<br /><br />The middle head is used for &quot;Medium&quot; speed signals.&nbsp; Any light other than red in here will have a &quot;Medium&quot; tag somewhere in the signal name.&nbsp; Red-Yellow-Red is medium approach.&nbsp; Red-Green-Red is medium clear.<br /><br />The bottom head is used for &quot;Slow&quot; speed signals.&nbsp; You see a light on the bottom, it will have &quot;Slow&quot; in the signal name.&nbsp; Red-Red-Green is slow clear.&nbsp; Red-Red-Yellow is Slow Approach.&nbsp; Now on NORAC Red-Red-Yellow is restricting, BIG difference in signal meaning there!&nbsp; But back to Seaboard signals.<br /><br />Now for the combination of heads:<br /><br />Outside of the straight medium clear/approach and slow clear/approach you will have a combination of lights on different heads.&nbsp; Its just a matter of &quot;building&quot; the signal using the heads.&nbsp; So a Yellow - green - red would be &quot;Approach Medium&quot;.&nbsp; Approach comes from the top yellow, and medium comes from the middle head being illuminated.&nbsp; Now a yellow-yellow is &quot;advanced approach&quot;.&nbsp; A red-yellow-green is &quot;Medium approach slow&quot; because you have a yellow on the medium head (Medium approach) and a clear on the slow head.&nbsp; It basically means you are taking a diverging route, and come up to the next route not exceeding slow speed.&nbsp; Which generaly means you will have either a slow speed signal or an approach on a short block.&nbsp; It gives the crew advanced warning.<br /><br />Now, anytime you see a lunar light, it makes the signal a &#039;restricting&#039;.&nbsp; Ditto with a numberplate or G marker on intermediates and a red signal that is a restricted proceed.<br /><br />The last thing we have to deal with is the &#039;flashing&#039; aspect.&nbsp; You&#039;ll only see this on the bottom heads.&nbsp; It just takes whatever the speed of that signal would be normally, and bumps it up one speed.&nbsp; So a Medium Clear becomes Limited Clear.&nbsp; Slow Clear becomes medium clear.<br /><br />Anyone with more interest can usually find CSX Signal Aspect and indication books on eBay for $5-10.&nbsp; They have drawings of the signals to help make this clearer.&nbsp; It includes NORAC and Chessie signals (B&amp;O CPL&#039;s and C&amp;O Color Lights)<br /><br />Basic Signal Card:<br />red-red-red : Stop<br />red-lunar-red: Restricting<br />yellow-red-red: approach<br />yellow-red-green: approach slow<br />yellow-green-red: approach medium<br />yellow-flashing green-red: approach limited<br />yellow-yellow-red: advanced approach<br />red-yellow-red: medium approach<br />red-flashing yellow-red: limited approach<br />red-flashing green-red: limited clear<br />red-green-red: medium clear<br />red-yellow-yellow: medium advanced approach<br />red-yellow-green: medium approach slow<br />red-yellow-flashing green: medium approach medium<br />red-red-yellow: slow approach<br />red-red-green: slow clear<br /><br />There are a few other signals involving &quot;S&quot; and other lights but you don&#039;t see those often enough up &#039;north&#039; here to worry about them.<br /><br />Practice Safe CSX 