For my final layout, I built a guardrail of 1/2" PVC pipe that was 3" tall and angled out from 45-degree fittings and sheathed with foam insulation. It may not have prevented derailments, but it definitely prevented damage.
Arnold, my layout was also 4' wide, and I used tubular K-Line 042 track on the outside and Williams 031 track on the inside, with K-Line 36" straights. All have close ties like prewar 072 Lionel. The 042 curves allowed me to run a scale Lionel Hudson, a Williams scale GG-1, and a Lionmaster PRR T-1. They might have looked a little awkward on the curves, but hey, they're toys, right?
