In Poland we still have the relatively medieval central radio and lights or semaphore system, tiered with rules to override it via radio plus really dumb automated braking system with train central detector, also enforcing speed limits in more advanced versions.
Plain old local moving block systems are widespread but US does not mandate them.
These are all mandatory (esp. the wired one where light or semaphore control is tied to NTC and/or PTC)
And the system is really dumb and electrical, not electronic. It is considered one of Automatic Train Protection systems. (The Polish short is SHP, translated as Automated Train Braking. The other system is Radio-Stop, a dumb radio alert system of local range triggered mostly manually forcing braking of all cabs in range.)
Similar slightly more modern systems are still used throughout Europe. The fact they are dumb (train is only slightly smarter) makes them cheap to deploy. They are mostly supervised or not automated other than the moving block light signal. (Which is often local and can be overridden at low speed only after radio confirmation.)
SHP is placed before speed limits and stations to alert the conductor. And if you pass the second one while the first is not cleared it means the train is runway and automated breaking is applied. The "logic" is in the train.
Compared to this Amtrak style PTC needs a big central computer system and control lines plus a train with an impressive array of sensors with remote data. Similar to ERTMS class 3.
US used to have legacy inductive systems in place, but for dumb cost saving reasons the companies were allowed to nor install them anymore.
Plain old local moving block systems are widespread but US does not mandate them. These are all mandatory (esp. the wired one where light or semaphore control is tied to NTC and/or PTC) And the system is really dumb and electrical, not electronic. It is considered one of Automatic Train Protection systems. (The Polish short is SHP, translated as Automated Train Braking. The other system is Radio-Stop, a dumb radio alert system of local range triggered mostly manually forcing braking of all cabs in range.)
Similar slightly more modern systems are still used throughout Europe. The fact they are dumb (train is only slightly smarter) makes them cheap to deploy. They are mostly supervised or not automated other than the moving block light signal. (Which is often local and can be overridden at low speed only after radio confirmation.)
SHP is placed before speed limits and stations to alert the conductor. And if you pass the second one while the first is not cleared it means the train is runway and automated breaking is applied. The "logic" is in the train.
Compared to this Amtrak style PTC needs a big central computer system and control lines plus a train with an impressive array of sensors with remote data. Similar to ERTMS class 3.
US used to have legacy inductive systems in place, but for dumb cost saving reasons the companies were allowed to nor install them anymore.