Has anyone got practical specs or design notes for track-bridge transitions that limit dip and ballast degradation at the abutments? I’m working a couple of open-deck steel spans (Class 3, about 50 MGT/yr, 286k) where the first 60 ft settles fast, and I’m weighing USPs/UBMs + crib compaction versus geogrid + shoulder widening per AREMA Ch. 5/15.
I’d prioritize a stiffness ramp — ‘ramp the stiffness, not the geometry’ — by grading USP hardness onto the span for 2–3 panels and running a thin UBM about 60–80 ft into the approach; that cut dip and ballast churn for us on a similar Class 3 steel deck. If settlement’s the driver, follow each tamp with a short prelevel and a dynamic track stabilizer pass instead of heavy crib compaction, so you don’t build a pogo stick. Got room to carry the mat full-width with >= 12 ft shoulders at the abutment, @OP?
Same pain here — the first 60 ft always wants to sink. Building on @lee39, what finally stuck for us was 30–40 ft of HMA underlayment (asphalt trackbed) from the backwall into the approach, then taper USP stiffness onto the open-deck ties; geogrid + shoulder widening per AREMA 5/15 didn’t last at about 50 MGT without that semi-rigid mat and solid backwall drainage. Can you get a short window to pave, or are you limited to ballast-only fixes?