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[quote user="Steve Raney"]A front-of-train air bag system shows promise in increasing rail safety. When inflated, the air bag system might be 15 feet long and 7 feet high. The system will be able to safely handle a collision between a pedestrian and a 60 mph locomotive, grabbing and holding the pedestrian until the locomotive comes to a stop.[/quote]   This airbag application calls for a permanently inflated airbag.  With a vehicle, the just-in-time inflation is triggered by impact of the vehicle against some obstacle, and then the airbag inflates to protect the occupant from colliding with the vehicle interior.  It has to be just-in-time inflation because there is no room for a permanently inflated airbag in the vehicle driver compartment.   <?xml:namespace prefix = o ns = "urn:schemas-microsoft-com:office:office" /><o:p></o:p> With a train versus pedestrian contact, there is no easy way to trigger the just-in-time inflation, and there is no reason for that approach because there is plenty of room for a permanently inflated airbag ahead of the locomotive.   <o:p></o:p> The proposal calling for a permanently inflated airbag says it will be fifteen feet long.  As the airbag deflects upon collision with a pedestrian, it acts like a spring.  That is, the resistance of the airbag deflection increases the further it is deflected or compressed.  During that phase of compression, the pedestrian must be accelerated from zero to sixty mph.   <o:p></o:p> During this phase of airbag contact and compression, the airbag will compress some amount before the pedestrian begins to move with the contact force.  Let’s just say that is five feet.  And then the pedestrian must be fully accelerated before reaching the front of the locomotive at the end of the airbag compression.  Let’s say that the pedestrian is fully accelerated by the time he or she is five feet from the locomotive.   <o:p></o:p> So the pedestrian does not begin to move until he or she is five feet into the airbag, and then must be completely up to speed by the time he or she is ten feet into the airbag.  So the pedestrian must accelerate from zero-to-sixty mph within five feet.  Even if protected from hard object impact, can a human body survive accelerating from zero to sixty within five feet?   <o:p></o:p> I think it is going to require a longer airbag; probably something in the neighborhood of 75-100 feet long.  Think what that will do for railroad photography.   This concept fits right into the pedestrian rights advocacy that seeks to empower pedestrians over motor vehicles.  It is a very European concept.  It includes advice such as encouraging your kids to play in the street as a means of claiming space and traffic calming.  What really amazes me is the fact that the FRA is involved with this nonsense.  Although it is not really hard to understand when you realize the game that is being played in the big picture.
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