Rail Shapes From Around the World.
Rail material has gone through a development cycle, from early wood, to iron and finally the steel in use today. Sleepers/cross-ties have had the same development, as wood, stone, pressed steel and other materials were or are used. Today formed concrete ties are the norm. Click to view many Rail Shapes
Rail Gauges around the world.
Many gages/gauges have been used throughout rail and railroad development. Some are refered to as "wide" gauges, and others as "narrow" gauges. These are relative terms, and the one in the middle could obviously be termed "Standard Gauge". Standard Gauge was an invention of George Stephenson of England. (He at times has been refered to as the Grandfather of Railroading.) His selected gauge was 4'-8" (!) Some argue that his gauge was actually 5' as measured outside the rail heads, thus the 8'6" inside measurement. However, as Stephenson wanted his locomotive/train to do more than travel in a straight line, like a curve, he widened his track gauge by 1/2" to 4'-8&1/2". Others developed trains using their own gauge, and the English/Metric systems did not help standardization. Further constraints for building the trackwork (mountains?) dictated the smaller gauges.
Enjoy the following chart (From the book "Transcontinental Train Odyssey" by Australian Tim Fischer.) Click to view a selection of Track gauges
Regarding the Internet story of the "Standard Gauge", it is said thought to have originated from the Roman chariot ruts in 2000 year-old stone city roads. Also, the perpetrated story that the Space Shuttle rocket dimensions are based on this dimension, or the "width of a horses arse..." Is it true or false? See Snopes.com railroad gauge discussion at: www.snopes.com/history/american/gauge.htm