Adding a maintenance walkway to the railroad bridge on my layout gate can not only increase the visual interest of the railroad bridge, but also narrow the space between the bridge and the plexiglass walls on the sides of the gate. While I wait for the plexiglass to be cut, I have been looking for a reference for the width of such a maintenance walkway and height of an outside fence on the walkway. I have yet to find such a reference and don’t know of a real bridge with a walkway that could be measured. References are welcome.