In the Early steam days the Roundhouse and Turntable was well suited for the maintainence of the Steam Locomotive. Each Locomotive could be parked in its own stall and the maintainence hungry locomotives could be serviced after every trip. The Turntable provided a convenient way of easily reaching any locomotive needed.
When Early generation Diesel began to appear in the Forty's with their MU Capabilities it was necessary to wye or turn these consists in a different way. Requiring less service, a run through shop was a lot more efficient. Most Consists were 3 or 4 or more Engines tied together with air and electric connections= MU. A wye track was a lot more convenient since these were longer and could hold more engines at one time when turning the consists.
By the late 50's most Roundhouses were fast disapearing, the exceptions being a few lines still running steam, such as the Durango and Silverton, etc. and short passenger or commuter lines since most of these lines only consisted of one or two engines at the most. Los Angeles's Redondo Roundhouse falls under this catagory, since most San Diegans only require one Engine.
Redondo's turntable can handle two F-40 or one GE and a F-40 at a time, and so it still survives. A new shop will be dedicated in August of this year. Their are no plans to Remove the Roundhouse at this time. Some say it should become a Historic site and I agree.
A lot of Roundhouses were downsized during the transition period, and some of these still exist today. UP's Cheyenne roundhouse still handles the 8444 and Challenger Engines, and UP's Vintage Diesel fleet. I believe it still, like Redondo is full size. I hope there are more examples in the Country today, since some of these should be preserved, for the new generation of train Enthusiasts that are growing up.
Sam Pottinger, Steel Rails West