From: nilknocgeo@earthlink.net   
      
   "bob"  wrote in message news:mc0a3e$6bo$1@dont-email.me...   
   > 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   
   >   
      
   This is obviously correct.  Good post.   
      
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