With clues provided by RSC, I believe I've nailed-down the reason for the glowing abutments for ScaleRoad bridges. The bridges are lofts with the abutments as child objects (start and end geometry) designed to cap the ends of the bridge. Apparently a bug exists in Railworks that renders the start geometry twice - basically two of the same object occupying the same space at the start of the loft, but the end geometry is unaffected. Not only does part of the object glow, but there's also a nasty z-buffer moire effect with the conflicting items. I first noticed this with the ScaleRail tunnel portals, but thought at the time it was due to a material issue. Nope, it's an RW bug.
Items affected include the following:
ScaleRail- Bridge Track (guardrail ends)
- Tunnel Track (portals)
ScaleRoadAfter months of trying to determine whether the models or my building techniques were at fault, I can go no further until RSC fixes this issue, which FWIW, has existed since the big RW3 update last year. The abutments, guardrail ends and portals can all be made as scenery items, but this adds considerable time for the route builder, as it was much more convenient to place these items automatically.
My apologies for any inconvenience.