can't be more precise because there are lots of different types and I can't guess from here which one you're dealing with

"This rail crossing structure is called a "frog" (in french, it's called "coeur de croisement"), and it looks amazingly like the burning man festival logo"
http://www.loupiote.com/burningman/photos/18424786.shtml

--------------------------------------------------
Note added at 11 mins (2012-06-14 11:32:05 GMT)
--------------------------------------------------

Termium:
"frog
CONT – A turnout is composed of a switch, consisting essentially of two tapered movable rails, designed to divert rolling stock from one track to another, and a frog, which permits wheel flanges to cross over opposing rails
Coeur de croisement
CONT – Les deux parties essentielles du branchement sont: a) l'aiguillage, composé principalement de deux rails mobiles qui font passer le matériel roulant d'une voie sur une autre; b) le coeur de croisement, qui permet le passage des roues à l'intersection des deux rails intérieurs.
http://www.termiumplus.gc.ca/tpv2alpha/alpha-eng.html?lang=e...

--------------------------------------------------
Note added at 13 mins (2012-06-14 11:33:46 GMT)
--------------------------------------------------

Lots of examples on Linguee:
http://www.linguee.fr/francais-anglais/search?source=auto&qu...