Even though the WP frequently didn't live up to its mythology, it did have pretty good track. Consider that the U30B's weighed up to 289,000 pounds. (Of course, they were mounted on trucks from retired F-units--which weighed much less--so they rode pretty rough.) On most any other units (especially six-axles), 60 mph on that jointed rail was pretty smooth. There was, however, a stretch of ribbon rail between Stockton and Sacramento that was restricted to 40 mph during hot weather because of potential sun kinks--once you got back on the old jointed stuff, the speed went back to 60 regardless of the temperature!