I see these every time a bicycle path intersects with any kind of car or train infrastructure. It just seems really patronizing, as if we’re not capable of slowing down without getting off the bike; it also shifts responsibility onto the cyclists if there is a crash based on something arbitrary (mounted vs dismounted).

There’s a short bike/pedestrian lane built near me to raise property values near some boutique stores–anytime it intersects the car road, there’s a sign to dismount. Message: you clearly aren’t riding your bike to get anywhere.
I also see it when a path intersects a railroad.
The railroad ones almost make sense depending on the conditions. At a level crossing which goes across the road at an angle rather than dead perpendicular, the groove next to the rails will catch your front wheel which may or may not result in you getting thrown off and/or winding up with a bent rim.
It’s not a problem if you’re paying attention. Assuming that most bike riders are paying more attention as compared to, say, most car drivers is probably still being unreasonably charitable. But in that case they’re unlikely to obey a sign, either.
The ones we have here spell it out with “angled rail catches wheels” and a picture of a ball headed safety dude getting bucked off of his bike rather than just blithely telling people to dismount.
Only if you’re riding through it completely not paying attention. I’ve got exactly such a crossing near my house, and I ride over it very frequently, both on a mountain bike and on a skinny-tire road bike. And I’ve never once had the slightest issue, because I pay attention to where the tracks are and momentarily go at an angle to make sure I cross over them more perpendicularly. Just takes a slight swerve at the right time, really.
I think the crossing I’m thinking of might be at a 30 degree angle or so, so that might be the logic there. But in that case: Caution Angled Railway would be more likely to result in actual caution instead of contempt.
I do remember a sign of bike crashes someone made for a city and all the hotspots were angled railway crossings.
Yeah I can’t even imagine. The bike lanes were I am at are on the street and constantly intersect other roads that also have other bike lanes. It would almost be funny to put one of these up as a joke but then I would worry some car head would think its a good idea.
Yes, it’s clearly some car-brained suburban shit from people who’ve never had to ride their bike to work.