There are at least five signs at eye level on the road leading up to the bridge, four of which are the standard yellow warning signs: https://imgur.com/a/owITLZC

In addition, the illuminated "OVERHEIGHT MUST TURN" sign flashes to attract attention.

I get what you're trying to say, but this bridge is better-marked than the vast majority of road hazards one might encounter. There's a certain point beyond which it doesn't make sense to keep spending time and money protecting people from themselves.

"OVERHEIGHT MUST TURN" is such a stupid phrase. It doesn't even mean what they intend: ”OVERHEIGHT! MUST TURN!"

Every time I drive through that intersection I’m amazed when I remember how fast most of the trucks are going by the time they get to the bridge.

And how's that working out for them? 100+ accidents?

The bridge just shrugs the hits off it is very tough. So the damage and the problems are really for the trucks not observant enough to see half a dozen warning signs and lights.

They are the ones who end up paying, not the railroad that owns the bridge.

There's a slightly lower heavy steel bar in front of the bridge to prevent people from hitting the bridge itself.