From: rcp27g@gmail.com   
      
   On 2015-02-17 16:38:27 +0000, Adam H. Kerman said:   
      
   > rcp27g@gmail.com wrote:   
   >> On Monday, 16 February 2015 16:25:47 UTC+1, Adam H. Kerman  wrote:   
   >>> bob  wrote:   
   >>>> On 2015-02-13 20:23:01 +0000, Marc Van Dyck said:   
   >>>>> rcp27g@gmail.com explained on 13-02-15 :   
   >   
   >>>>>> or putting in positive singalling control on others (ie where the   
   >>>>>> crossing is protected by railway signals that aren't cleared for the   
   >>>>>> train until the barriers are down and the crossing positively checked   
   >>>>>> to be clear).   
   >   
   >>>>> This is perfectly feasable but requires to order the gates to go down   
   >>>>> at a distance that is longer than the braking distance of the train.   
   >>>>> This means there will be a long delay between the gate going down and   
   >>>>> the train actually passing the grade crossing.   
   >   
   >>>> Indeed, this is the case.  It is less convenient but allows for   
   >>>> positive safety.   
   >   
   >>>>> As it has been mentioned,   
   >>>>> motorists are unpatient creatures; if the delay is too long, people   
   >>>>> think the gates are faulty and start turning around them. You might end   
   >>>>> up this way with a grade crossing that is inherently less safe, because   
   >>>>> of human nature...   
   >   
   >>>> Solved by making the barriers block the whole road.  As the crossing is   
   >>>> positively checked to ensure the barriers are down and the crossing is   
   >>>> clear before clearing the signals for the trains, the issue of cars   
   >>>> being trapped within the crossing is avoided.   
   >   
   >>> Clearing level crossings several minutes before the train arrives mitigates   
   >>> against non-existant risk, and it's quite labor intensive. How is the   
   >>> cost of delay justified? How is the personnel cost justified?   
   >   
   >> This "non-existant risk" just killed 6 people.   
   >   
   > You know, I really can't stand people on Usenet who can't debate, and   
   therefore   
   > find it necessary to set up a straw man.   
      
   Pot, meet kettle.   
      
   > She didn't violate the grade crossing minutes before the train arrived, but   
   > within the last 15 seconds. She had a minor intrusion at about 15 seconds,   
   > then at about 5 seconds, pulled deliberately into the path of the oncoming   
   > train.   
      
   You are contending that people will violate a crossing regardless of   
   the state of barriers across the roadway blocking access to the   
   crossing.  I contend this is not the case.  In the collision in   
   question here, the barrier came down *on top of* the vehicle.  That   
   means the vehicle was *already* inside the crossing (as defined by the   
   area bounded by the road barriers) *before* the barriers came down.  I   
   would suggest that, while some drivers will enter crossings with the   
   barriers up even if the lights/sound warnigns are active, and will   
   drive around partial barriers (plenty of youtube videos show this   
   taking place), they are far far less likely to drive *through* a   
   barrier that is blocking the road.   
      
   > The system you advocated addresses a period of minutes before the   
   > train arrives in which there really isn't any danger of collision.   
      
   The difference between the crossing types I have described is not down   
   to the method used to keep cars off the crossing, but the method used   
   to keep *trains* off the crossing.  In the crossing involved in this   
   collision, there is *no* method to stop trains from crossing.  If the   
   train arrives at the crossing, the first indication they have that   
   something is not right is when they are so close to the crossing   
   itself, there is no chance to stop the train.  In the crossing I have   
   described, the railway signalling system *blocks* trains from the   
   crossing until *after* the barriers are down *and* the crossing is   
   observed to be clear.  Only after that has taken place is the train   
   permitted to cross.  Once the train is given permission to cross, the   
   only way for a road vehicle to violate the crossing is to *break   
   through* a physical barrier blocking the road (the whole road, so no   
   option to zig-zag around the barriers).  In a situation in which   
   something unexpected takes place, like a barrier drops on top of a car,   
   the train will not yet have permission to enter the crossing, so a   
   collision can be avoided, regardless of how sensibly or stupidly the   
   driver behaves.   
      
   Robin   
      
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