Since many of my earliest trails miles were put in at Jacobsburg, I've been interacting with equestrians for more than ten years.
For a portion of that time I admit to being clueless.
I recently attended a trail-building seminar where there were many equestrians present, so I had the opportunity to get the word straight from the... (really bad joke). Here are a few hints you might find helpful when riding Jacobsburg, Blue Marsh or any other place that welcomes equestrians.
Let me start by saying that it's my personal opinion that, in general, local equestrians are very cool with cyclists. And they do really appreciate your taking the effort to show them a little courtesy. It only takes one bad experience for folks to leave with a bad opinion of cyclists.
For those who don't already know it, multi-use trails system require that cyclists yield to everyone else. It's not gonna' ruin your training loop to be friendly and wait for a minute while a horse passes -- and a good relationship far outweighs this minor inconvenience.
It seems that all potential issues really stem from the horse being spooked, so a lot of this is common sense based on that fact...
• Make your presence known by greeting them calmly as soon as possible (not so far away that you need to scream) and ask the rider for instruction on how to proceed. I'm told that the rider interacting with you vocally can help to keep the horse calm. Though opinions seem to vary on using a bell, the local folks I spoke with really prefer talking -- and squealing brakes are not a reasonable alternative to this. By the way, this goes for hikers as well. Don't be shy! speak to people from a distance and don't just yell, "on yer left!" I've actually seen people jump to the left when they hear this.
• Unless the equestrian tells me differently, I stop the bicycle and dismount, standing off the trail. In general, whenever you stop on a trail -- you should get off the trail.
• When possible, stand on lower ground than that of the horse.
• Don't look the horse in the eye. Evidently, they view themselves as potential dinner and are intimidated by any animal with forward facing eyes that stare at them.
• If you typically ride with ear buds, consider keeping one out so you can hear if someone is trying to talk to you. Again, relationship building.
Much more info on this stuff is available from IMBA.
Thanks for reading. Hopefully I was able to share something you didn't know before.