In 1997, there were nine Class I freight railroads (railroads with operating revenues of over $256.4 million). These railroads accounted for 71 percent of the industry’s 274,399 km (170,508 mi) operated. There were 35 regional railroads [those with operating revenues between $40 million and $256.4 million and/or operating at least 560 km (350 mi) of railroad]. The regional railroads operated 34,546 km (21,466 mi). Finally, there were 513 local railroads operating over 45,300 km (28,149 mi) of railroad. The elements that are subject to corrosion include metal members, such as rail and steel spikes; however, corrosion damage to railroad components are either limited or go unreported. Hence, an accurate estimate of the corrosion cost could not be determined.One area where corrosion has been identified is in electrified rail systems, such as those used for local transit authorities. Stray currents from the electrified systems can inflict significant and costly corrosion on non-railroad related underground structures such as gas pipelines, waterlines, and underground storage tanks.