In Nickels v. Grand Trunk W. R.R., 560 F. 3d 426 (6th Cir. 2009), the Court of Appeals for the Sixth Circuit held that railroad employees' negligence actions were precluded because 49 C.F.R. 213.103 covered the issue of ballast size. The issue in Nickels involved ballast used for track support, not ballast used in other areas of the rail yard or on walkways. Id. In Nickels, 560 F.3d at 428, railroad employees claimed "that their former employers failed to provide a safe working environment by using large mainline ballast--instead of smaller yard ballast--underneath and adjacent to tracks receiving heavy foot traffic." The railroad employees argued that the employers "could have used smaller ballast in areas of heavy foot traffic without violating their duty to provide a stable track." Id. at 431. The Sixth Circuit held that 49 C.F.R. 213.103 substantially subsumed the issue of ballast size used for track support, making no distinction between mainline and secondary track, and found that the regulation leaves the size and type of ballast to be used up to the "railroads' discretion so long as the ballast performs the enumerated support functions." 560 F.3d at 431. Tellingly, the Sixth Circuit made the following observation as to the railroad employees' claims: The railroad employees note that 49 C.F.R. 213.103 does not address "what constitutes a reasonably safe walkway for railroad employees performing their duties adjacent to the track." This suggests that the railroad employees allege negligence in the railroads' use of oversized ballast in areas completely separate from those where track stability and support are concerned. Such an allegation, however, does not appear in either of their complaints. Nickels alleges that "railroad ballast" was used by the railroad to support the railroad track. . . . Even to the extent that the railroad employees argue oversized ballast was used "along," "adjacent to," or "parallel to" the track, they do not contend that the ballast in those areas was not being used for stability under 213.103. (560 F.3d at 432-33.) The holding in Nickels was premised on the observation that the employees did not contend that ballast used on walkways was not used for stability, in other words for track support. Id.