Basically it is that simple.
See Kelly's following post for an explanation as to "How". I'm giving you the "Why".
In spite of what Fairlie wrote in "The Battle of the Gauges", as Broad gauge equipment became larger, the smaller gauge equipment couldn't keep up. Remember, the Railroad charges on the ton-mile and as Standard Gauge loads became heavier and heavier, the 3' gauge was put into a more and more precarious financial situation because if its higher Tare (Dry) Weight per car. In other words, it cost more to haul freight on the 3' gauge.
What does that have to do with loco size? Simple... if you have to rebuild your right of way to accomodate larger, taller equipment, why not go either whole hog and Standard Gauge it and save the Freight Transfer costs or just scrap the line as unprofitable? Unfortunately for many of the roads with smaller equipment, scrapping was the first option. In the D&RGW's case, they just went with locomotives that would fill out the clearance requirements and strengthened the bridges to accomodate them.
For a graphic example, look at the problem between Gunnison and Montrose (Cerro Summit, if I remember correctly, if I don't Jerry Day will correct me). Running a K-27 was prohibited in the Black Canyon because of the clearances. The largest locomotive allowed was a either a C-21 or C-25. I'm not a D&RGW afficionado so I'm trying to remember as best I can here. By that time, however, the Tennessee Pass line was broad gauged and handling the transcontinental freight. The D&RGW didn't deem the Gunnison line worth the extra expense to Broad Gauge or upgrade except from Gunnison on because of the CF&I COal Traffic. Hence, the line was scrapped by 1955.
Remember, SP, a Railroad is a business. Businesses are there to make money. If the portion of the business does not make money it is either sold, closed or dismantled. With the 3' gauge, it was put behind the eight-ball because of its small size and the abandonment petitions were put up for any reason, real or imagined. Believe me, except for certain individual employees, there are no altruistic motives in operating a Large Railroad. It is always the bottom line. If the 3' gauge isn't pulling its weight financially, no matter how scenic it is, its days were numbered as part of a large Railroad.
Rick
