Rail operators are occasionally able to get waivers from the FRA to run non-compliant rolling stock. Caltrain was awarded such a waiver for a future rolling sto

Rail operators are occasionally able to get waivers from the FRA to run non-compliant rolling stock. Caltrain was awarded such a waiver for a future rolling stock purchase, and the Sprinter was awarded one as well. Typically the FRA requires that there be some sort of temporal separation between the trains, which could mean freight only running at night, or it could mean all trains on the line have some form of electronic PTC (positive train control) that guarantees separation between trains. The freight lines have been fighting PTC for several decades, but they're finally being forced to implement it (of course the FRA hasn't set much of a standard, so there's going to be a dozen different incompatible systems, yay). The problem is that the waivers are arbitrary and one-offs. There's no standard for light passenger rail in the US, there's just a bunch of hyper-specific waivers for each case and operators must re-apply if their rolling stock changes. So if caltrain wanted to switch from UIC-compliant Siemens Desiro trains to a UIC-compliant hitachi train, they'd have to apply for another waiver. To top it all off, the FRA's own studies showed that their "buff strength" standards are more dangerous than the more modern energy-absorbing crash structures mandated on European and Japanese lines. The FRA really does need to be reformed.