It's truly sad that the US averages about 6 collisions per day at RR crossings with several hundred fatalities each year 
http://oli.org/about-us/news/collisions-casulties
The numbers seem to be on a downward trend perhaps in part because of better coordinated signaling technology. Thus, I think it's worth $1 in parts and effort to include this in your layout if appropriate.
Again, it depends on how you trigger you crossings, but a general solution would be an opto-isolator which "shorts" the capacitor when a train triggers your crossing gates/signals/flashers. I suggest the LTV-8141 opto-isolator only because GRJ showed it in one of his circuits, DigiKey sells it (64 cents qty 1), and if you're only going to "stock" one opto-isolator in your stash it's a good one to have for O-gauge applications. So by applying, say, 12V (AC or DC) to the opto-isolator thru a current-limiting resistor, the capacitor is discharged which resets the 4017 and the E-W traffic gets the red light as long as the train is present.
