Car Bridge Question.  For those of you setting up bridges.  What is the minimum and maximum distance between rails.  I have on a number of trips had to cross these bridges on my atv.  This requires riding on top of the rails. It has been hairy on a few occasions.  Do you have a set distance that you try and follow?  Has anyone thought of placing them a little closer together to allow for easier atv access.  It always seems as if there is plenty of room to accommodate my  fullsize truck.