jjtrains:My wife and I just de-trained from Amtrak #1, the Sunset Limited, at Palm Springs, CA this morning a few minutes early. Yesterday, the run across southwest Texas, New Mexico and Arizona was made in 99 to 106 degree F temperatures with no speed reduction. Top speed was 82.6 mph with a lot of 79 mph running. Was wondering how the U.P. handles the "speed kink" problem on the ex-S.P. mainline so as to not require speed reductions. Amtrak #1 ran ahead of schedule the entire way. (We were actually in the #421 sleeper from Chicago, switched at San Antonio from the Texas Eagle to the Sunset Ltd.)
The quick answer is that as long as your track structure is designed, built and maintained to a high standard, sunkinks are unlikely to occur and there is no need to issue slow orders in hot weather. But of course this requires that management allocate the necessary resources to the track department, which the stock analysts may not like. And, there must be enough traffic on the line to justify such expenditures, which is why these "heat slows" are more often found on secondary mains and branch lines.
John