Some of you guys may find these helpful.
When you need bridge ties and rail for a bridge that you've built and it doesn't come with ties molded in place, or doesn't supply the track for it, Micro Engineering makes flex track with bridge ties attached, and guard rails included in the package. You can attach the track in place with a slow curing gel CA.
If you prefer to handlay the track, using real wood ties, obtain some bridge ties from companies like Campbell, Kappler, etc. Stain these an appropriate color and attach these to the bridge, or trestle with a contact cement, white glue if a wood-to-wood attachment, or a slow cure gel CA. After these are in place, take the rail, cut to an appropriate length, and smear Walthers Goo, onto the underside of the rail. Using several 3 point track gauges, place the rails in proper position on the ties, and slightly press the rails against the ties.
Then take a hot 40W soldering iron, and slide the iron across one rail slowly. As the iron heats the rail, it will fast cure the goo, and the rail is held securely in place. Then using the track gauges again, repeat across the other rail keeping the rail in gauge with the other.
After this, using a smaller code rail, do the same thing for your guard rails on the inside of the running rails and make sure that there is enough clearance so the bases of the guard rails don't touch the base of the running rails. For curved bridges, I would increase the distance between the running rail and the guard rails so a long engine truck or a steamers drivers won't touch the guard rails while crossing the bridge. Make sure the guard rails are longer than the bridge, and bend the rail ends to form the "pointed end" of the guard rails. They don't have to touch at the ends, but they do look better if they do.
The Goo will hold the rails in place indefinitely, the joint is very strong, and it will allow for the rails to expand or contract without breaking the attachment to the ties. While this sounds like a lot of work, anyone who prefers handlaid track will find it an excellent way to attach rail to a bridge, without having to spike the rail in place, and risk splitting the ties.