Gantlet track

I was reading the latest issue of MR and a article on "two independent tracks cross a narrow bridge by having a “gantlet” type track that partially crosses over and run inside the other. Can someone tell me how to construct this and possibily have a picture accompany it.

Goodle may be your friend, but I got this one from Bing

There are no switch points, just a frog. Signals control access.

Here is another version: it has switch points but no frog. It allows a passenger train to stop at the station, yet allows freight trains to fly by with less width restrictions.

ROAR

gantlet_zpsb783bde6 by Donald Schmitt, on Flickr