Four feet, eight and one-half inches.
That measurement automatically means something to a few of my readers (mostly nerdy old guys like me, I'm sure) but will leave most of the audience baffled until I explain the purpose of such a specific distance. Four feet, eight and one-half inches is the standard inside span between two railroad tracks in most of the Western world.
Now, the favored legend of how 4' 8.5" became the standard gauge for railroads is literally Romantic: James Stephenson, the inventor of the locomotive, built his first railroad in old Roman chariot ruts, which also happen to be that magic distance. The pedestrian truth, though, is that coal mining wagons typically used 5'-wide axles. The axles were attached at the outside of the 2"-wide wheels, making the wagon's tread width 4' 8" from the inside of each wheel. Add a 1/4" wiggle room to the rails so the flanges of the wagon wheels could easily turn corners, and -- boom -- a standard gauge is born.
Just because the gauge was "standard" doesn't mean it was universal. By reason of geology or economy, the standard gauge wouldn't fit in places such as mountain railways or winding valleys. The Denver & Rio Grande Western, for example, relied on a 3' gauge for much of its pathways through the Rockies. Many logging railroads of the Northwest chose the 3' gauge in order to slide narrow flatcars around the pine-covered hills.
Sometimes, odd gauges were chosen for defensive reasons. The Soviets, for example, have a gauge of 4' 11 and 5/6" -- which slowed invasions by Germany during two wars. Gauge choices can also be defensive in an economic sense. Many trolley car lines, fearing hostile takeovers by freight trusts, deliberately built their rail systems in wider gauges, on the premise that their networks would be unappealing to the robber barons.The most common trolley car gauge was five feet, two and one-half inches. It was called the "Pennsy Gauge" because the first trolley lines to adopt the odd width were located in Pennsylvania.
The Pennsy Gauge is still used in, well, Pennsylvania of course (most of their subway and trolley lines use the five-foot-two-plus width). It's also used in the few towns still operating 100-year-old trolley systems -- like New Orleans, for instance.
I was in The Big Easy this past week, and had a chance to be a total rail geek tourist with their trolley system. Sadly, there's no streetcar named Desire anymore - - the Desire Street Line was closed in 1948. There are still three operating lines in the city, though: the Riverfront Line, the Canal St. Line, and the St. Charles Line. St. Charles uses Perley A. Thomas streetcars built in 1923. Eighty-eight year old street cars still manage to haul over 17,000 passengers every day through the streets of New Orleans.
Here's a picture of two gauges: on the left is the 5' 2.5" Pennsy Trolley gauge, and on the right is the 4' 8.5" standard gauge. The two rails parallel each other on the riverfront, with freight trains taking the rightmost rails and streetcars using the left.
A better view of the wide Pennsy gauge running down the "neutral ground" of the St. Charles median. Very odd and scary to see folks jogging along an active trolley line, but people were using this center grassy strip as both a rail and a trail.
The wide gauge certainly makes for a wide interior. Four across still leaves room for two average-sized people to stand side-by-side in the aisle.
The wooden seats and the brass fixtures are authentic. According to the motorman, they're original to the trolley.
It's a beautiful thing to see a piece of railroad history actually doing a day's work instead of sitting parked in a museum. I'm glad the New Orleans Transit System picked the wide Pennsy gauge to keep these trolley lines from being swallowed up by some now-bankrupt railroad company. That defensive move let me take a ride on a streetcar named St. Charles a whole decade into the 21st Century.