I'm not sure what the "correct" method is, but I.......

.......have the bridge track rail extend about 4" beyond the end of the bridge (in O scale-hand laid) and this is secured with glue for the ties, spikes and rail joiners.  (glue only if using flex track) The bridge itself is not secured to the abutment but the "feet" rest on it.  This makes it relatively easy to remove.  Slide the rail joiner back, unspike the rail and lift off.

Peter 

I fix the bridge in place to

I fix the bridge in place to ensure it won't shift under weight or due to slight inadvertent bumps.  First, though, I ensure the tracks will sit on it at grade along its length and beyond to where the rails join the tracks on either end.  I don't want bumps and gaps and any rolling. 

Once I have the bridge glued into place, and its piers/bents supported properly with artificial terrain or mud sills, I lay a length of track that is longer than the bridge deck, usually for several inches longer as Peter described previously.  Care must be made to keep curved approaches nicely radiused.  The glued ballast leading up to the bridge will help to anchor the tracks on the bridge and the bridge itself if the tracks are glued to the bridge deck or the trestle's stringers.  Once all is firmly established, I fashion inner guard rails for the bridge deck and glue them into place.

What I do

I normally build the scenery shell first, then secure the abutments in place.

The abutments are shimmed as needed to ensure the track on the bridge lines up with the track on the adjacent roadbed.  Note how the rail joints, visible at this stage, are a few inches from the abutment.  I prefer keeping the joints away from the bridge so I can minimize any bumps that may occur if the bridge and rails join with the rest of the roadbed and track at the same place.  I used wood ties between the bridge and the rail joints.

After the scenery mess is almost done, I install the bridge by dropping it in place on the abutments, and spiking the rail to the ties on either side.  The bridge itself isn't secured, only the rail.  Track weathering and ballast hide the use of plastic and wood ties so they all look essentially the same.

This bridge was handled a bit differently.  I installed flex track across the future span, and cut the plastic ties out later.  Like the above bridge, this one has wood ties.  I shimmed the abutments and bridge up to the level of the rail, then spiked the rail in place across the bridge.  Again the bridge just sits there, held in position by the rail spiked to the ties.

This steel trestle uses Micro Engineering bridge track with plastic ties.  I stripped the ties from either end, and spiked them to wood ties, again to keep the rail joint a few inches from the bridge.  In this case, the towers with their concrete piers are glued into the scenery, but I still didn't glue the bridge to the abutments.

Bridge Abutments

I like your bridge abutments, are they custom made?  If so can you describe how you made them.

Re: JamesS

All the bridge abutments in my photos are scratchbuilt from styrene sheet.  I start with photos of prototype abutments and adjust the proportions to fit the available model bridges.  It's not very scientific.

Good Info

Gents,

Thanks for your help and advice on this.  I shall proceed with my project.