First, the good news is that your horse is great about everything else. This suggests that he can easily learn to comply with novel or threatening situations and tasks. Otherwise, there would likely be some other aversions in his domestic life. It also suggests that he is genuinely fearful. If he is one of those characters who is just "testing you," it would have shown up somewhere else by now. As with helping an adult horse overcome aversion to anything, such as trailer loading, bridge crossing, stocks, clippers, blankets, injections, feet handling, rectal temping, and so on, the training is usually more effective if done as an independent teaching project, where there is no big pressure to complete the task. The focus can be on the training procedures and on how much progress is made with each session, rather than on the fact that he failed to cross again, and in doing so ruined your nice ride. It’s also amazing how little time it takes to gain compliance when that one task is all you are doing.

So, what exactly would you do? Well, it sounds like overcoming this problem is pretty important to you and might be worth some initial time and effort for an almost guaranteed good outcome and continued compliance. I would get some railroad ties and rails, then set up a mock railroad bed somewhere familiar to him on his home farm. It’s good to place the obstacle where the horse must pass on his way to somewhere he likes to go, or at least is used to going.

For example, most horses like to go out to pasture, or at least are familiar with the procedure and safety of the pasture. If that is the case for your horse, you can set up the rails and ties on the ground at the gate into the pasture. If he won’t lead across for you, make a safely fenced chute or pen enclosure leading into the pasture gate. Just release him into the chute or pen, close it up behind him, and let him cross over the rails through the pasture gate in his own time. If he hasn’t crossed after a few hours, increase his attraction to the pasture. You can do that by putting water and grain just a few feet inside the pasture. Or if he has a favorite horse companion that is not afraid of railroad tracks, you can bring the other horse or horses up near the gate or you can walk the other horse back and forth through the gate (over the mock railroad bed). This will entice your horse to join the others and reassure your horse that "it’s no big deal." (Be sure to familiarize the companion horses to this novel gate railroad arrangement ahead of time so they don’t send any fear signals to your horse