For those of you that can't understand the obvious disdain for anything diesel (regardless of gage) on this site - please understand that their interests and opinions are generally far narrower than the gage. I personally don't care that much for traction, but understand that it is part of railroad technology. For that matter I'm turning into an old fart and don't necessarily "appreciate" the modern techno-electronic control garbage. For steam, I don't get to appreciate it as much because it comes with far too much political baggage and rabid foaming steamies. (A minority, but far too many in proportion tot he noise they create.)
The best example is when we are lucky enough to see a big engine out on the main, the first complaint is about the diesels behind the steam engine. Guess what? The railroads can't afford to have the entire division slam to a halt if something goes wrong, the needed fuel and water facilities to run steam only don't exist (hence the diesels typically do most of the work to conserve steam's fuel and water) and there is hardly anyone in the US that can run a train down a heavy grade without working dynamic brakes. But don't worry - since Amtrak just killed off their charter train business the only mainline steam we might see is going to have to be sponsored by the railroad it is operating on, and there aren't too many of those willing to.
This is kind of like religion and politics - there are too many in this hobby (and world) that are more than willing to condemn the rest of us to hell for not believing exactly as they do. I just like railroad history and technology, and some parts of it interest me more than others.
As far as North American narrow gage:
There was simply too little narrow gage compared to the rest of the standard gage on the continent to survive. Brazil doesn't even have standard gage that I know of - either meter or 63". The Philippines (except for some plantation trams), New Zealand and South Africa all built extensive "Cape gage" systems at 42". Japan was primarily 42", but I think the newer stuff (bullet train?) is standard gage, though I'm not sure where they are on converting freight lines. Didn't Australia have 42", standard and a third gauge at one time?
In North America, there were remaining pockets of common carrier ng lines left when dieselization hit here in the 1950s. You had the D&RGW, WP&Y, SP in the Owens Valley, Newfoundland and some in Mexico. All of them dieselized except the D&RGW. The reason was simple economics. New diesels were extremely expensive, but could pay for themselves due to reduced operating and maintenance costs. GE had their salesmen actually cost out how long the diesel replacing steam would pay for itself. Look at White Pass - they were buying new steam locos after WWII, but even they couldn't ignore replacing them with diesel. It took longer for third world countries to replace steam for several reasons. Labor was cheap (and often a government job) and most of the repairs could be done in house using common materials. Diesels required specific parts both for the engine and the electrical system, but in North America you still needed injectors, air compressors, lubricators, etc. and as the steam appliance manufacturers started to fail (or raise their prices to keep from failing) it was going to become even harder and more expensive to keep running steam.
Think about how many narrow gage operations even exist. The original D&RG main that was standard gaged between Grand Jct. and Salt Lake is just a shadow of itself, Monarch is long gone, and once the pipe was gone there was no reason to keep Cumbres open. D&RGW likely considered diesels in the 1950s, but even they couldn't get the numbers to pencil out because the lines were simply going to fail due to lack of traffic. Newfoundland is entirely gone. If it weren't for the cruise ship industry the White Pass would be abandoned. SP bought the #1 designed to be converted to standard gage, so they even knew that it was only a matter of time. It was only needed about 6 years, but was long enough to justify its investment and be able to prove to customers and the ICC at abandonment that they had tried to modernize and reduce operating costs. Between the implosion of the US steel industry and conversion to other methods, is there even any narrow gage steel mill rail operations left? Arkansas Lime standard gaged, and US Gypsum still manages to survive - until the day they either shut down or can economically replace their narrow gage operations.
Honestly the biggest threat that finally ended the narrow gage in North America was the public road system, trucking and the private automobile. There was no longer the requirement to use public rail transportation for passengers, mail and express - it all went to road (or air). For the most part, what a narrow gage freight car can haul so can a modern truck. And as mining and other traffic patterns shifted it simply became more economical for trucks to take over the business. Look at the central American countries that used to have extensive rail networks for common carrier and plantation use - almost all has gone to truck and bus. INCOFER in Costa Rica seems to be the exception, the operations around San Jose are expanding for commuter service because he government is willing to invest in rail versus road because of fuel efficiency.
Don't blame the diesel for the loss of steam - blame progress - and you can't stop it.
