We are resurfacing track over two 60-ft steel girder spans and keep chasing a stubborn approach dip even after new ballast and 18 ft of undercut. Has anyone had better results with a longer approach transition or under-tie pads to smooth the track modulus jump at the bridge seat? I’m leaning toward 115RE CWR with 24 in tie spacing and a 1:600 vertical transition, but maintenance wants to keep jointed rail for easier bridge work — what’s held up for you?
On two 60‑ft girder jobs we beat the ‘approach dip’ by installing 8–10 mm under‑tie pads for the first 60 ft from the backwall on each approach and doing a light retamp a week later; it softened the modulus jump more than a 1:600 alone. If you stay with 115RE CWR and 24 in spacing, that pad zone has been enough for us without lengthening the transition. Any chance your ‘18 ft of undercut’ stopped short of a wet pocket tight to the wingwall?
I’d stretch the vertical to 1:800 and use a thin approach ballast mat that straddles the backwall (first 30–40 ft on deck and 40–80 ft on approach); that smoothed the modulus jump for us on 60‑ft girders. Keep your 115RE CWR with 24 in spacing, but plan a retamp after about 2 MGT and consider a grouted shoulder the first 20 ft to resist pumping. @lee39’s pad idea is good, but the continuous mat avoided tie roll for us — do you have room to extend the undercut beyond 18 ft if the subgrade’s soft?