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New story on the Northridge Metrolink crash.

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 Ed, Thanks for that explanation of the constant yellow (approach) versus flashing yellow (approach restricting) aspect.  I knew what approach meant, but I did not know what approach restricting was.  I want to understand what role these two preceding signals played if the final signal were green.  I am still not sure if I quite understand your explanation of the scenario.  For instance, you say that even if the final signal were green, the engineer would have to approach it at restricted speed because of being delayed in block.  Yet I thought the delayed in block meant that he had to approach the next signal prepared to stop in case it was red.  That is what the Trains article said.  Since he could see the green signal from the station (if it were green) he would have known it were green, so why would he have to approach it prepared to stop in case it were red? <?xml:namespace prefix = o ns = "urn:schemas-microsoft-com:office:office" /><o:p></o:p> This is how I understand it: <o:p></o:p> Sanchez may not have violated either the flashing yellow or the following constant yellow as he approached the station and stopped, taking into account a slowing as he prepared to stop.  So, the only issues of signal compliance came after he left the station.  At that point, the issues would pertain to the aspect of the next signal and of the last signal, which was constant yellow or approach. <o:p></o:p> When he passed the flashing yellow, he was required to not exceed 20mph until passing the next signal.  That signal was constant yellow, so when he passed that constant yellow, the requirement of the flashing yellow expired, and was replaced by the requirement to approach the next signal prepared to stop for it should it be red.   <o:p></o:p> In addition to the “approach” requirement imposed by the constant yellow, was a duplication of the “approach” requirement imposed by the fact that he was delayed in block by the station stop.   <o:p></o:p> So, while standing at the station—  <o:p></o:p>IF THE FINAL SIGNAL WAS RED:<o:p></o:p> <o:p></o:p> 1)      The engineer has a red signal within his sight. 2)      The engineer has passed an approach signal, which told him to be prepared to stop at the next signal. 3)      The engineer is considered delayed in block, which tells him to be prepared to stop at the next signal. <o:p></o:p> So there are three independent reasons why the engineer should be prepared to stop at the next signal.  <o:p></o:p>IF THE FINAL SIGNAL WAS GREEN:<o:p></o:p> <o:p></o:p> 1)      The approach requirement imposed by both the previous constant yellow signal and the delayed in block status has expired. 2)      Because the engineer can see the green signal while standing at the station, he is free to leave the station and accelerate to track speed.
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