Caltrain plans to use lighter electric multiple units that do not comply with the Federal Railroad Administration (FRA) crashworthiness standards, but instead comply with the International Union of Railways (UIC) standards, on the electrified lines. The FRA granted Caltrain a waiver to operate these units, which were previously banned on mixed-use lines with other FRA-compliant rolling stock due to concerns over crashworthiness, after Caltrain submitted simulation data showing UIC-compliant rolling stock performed no worse or even better than FRA-compliant rolling stock in crashes. Caltrain plans to retain its newer diesel-electric rolling stock for use on the Dumbarton Extension and service south of Tamien.