I’m seeing multiple Class I bid packages this quarter specify USPs on tangent and 2° curves, with target tamping intervals >24 months and a claimed 20–30% ballast life extension — anyone else revising standards? We’re trialing 10 mm elastomer pads under 136RE CWR with 12 in granite ballast near MP 47, and our geometry car passes after about 60 MGT show a about 30% drop in vertical variance compared to control.
Same trend here: moved USPs from pilots to program on tangent and up to 2°; after about 60 MGT we’re seeing 25–30% fewer surfacing hits, but , we had to bump shoulders to 18 in and tighten clip torque to hold gauge in heat… One tweak that helped: spec a stiffer pad on curves (step up one stiffness class) and dial tamper squeeze down so you don’t scuff the pad. With your ‘10 mm under 136RE, 12 in granite near MP 47,’ how’s drainage — any mud pumping or WILD data to back that 30% v drop?
Quick datapoint: we went to 8 mm USPs on tangent and up to 2°, and stretching surfacing to about 30 months only worked after trimming tamp squeeze about 15% and capping lifts to about 1.5 in per pass — think of the pads as track sneakers, don’t scuff them… Best ROI was at bridge/culvert approaches; sleeper accel dropped about 20% by 50–70 MGT, which matches Pandrol’s notes: Resilient Under Sleeper Pads for Track Vibration Attenuation | Pandrol. Are you seeing a winter stiffness bump with the 10 mm, or holding modulus steady through cold snaps?