Some cities allow trains to refrain from horns within city limits and instead the barrier makes a more localized dinging. I live near a major rail interchange and they rarely every honk their horns, oftenly only using a short warning horn if needed.

When I lived rurally trains with horns were far more common. On a human note I'd rather hear a train horn occasionally than hear constant traffic noise. I get how thats harder to manage with a dog but perhaps consistent training could lessen their response to horns.