Trivia

[Basle6]

Where in the world is it possible for a boat to sail under atrain travlling under a car driving under a plane?

[lector]

the order seems to be (top down)

Plane
Car
Train
Boat

A double-decker bridge on a plane path!

eg. Tsing Ma Bridge and Kap Shui Mun Bridge in Hong Kong have six lanes on their upper decks, and on their lower decks there are two lanes and a pair of tracks for MTR metro trains.

[maxi2]

Windmill Lane, Southall, Middlesex is the site of the "Three Bridges Ancient Monument" created by Brunel. Here the road goes over the Grand Union Canal and the Great Western Railway goes underneath both at the same spot. So not quite the same as your question but close!

[Petal]

Britannia Bridge, Menai Strait?

[maxi2]

Petal has a better answer than mine - the right one I think!

[pjwillcox]

the Oresund bridge between Denmark and Sweden is next to Kastrup (Copenhagen) airport, it is double-decker with car on top and train underneath