TCAS has solved this for airplanes. It wouldn't take much to modify the system for trains so that, in the least, it notifies when an unexpected train is nearby. A little more logic could allow it to verify which track each train is on.
1. Planes can determine their altitude. Trains don't know which track they're on. You'd have to re-engineer existing signalling systems designed around the inverse. Track transponders and axle counters know which trainset passed a specific piece of track, but the trains don't know which track transponders link together on the same track. They don't even know which track they'll be going down next because that's up to the signallers controlling the points, not them.
2. Planes fly in the air and can send omnidirectional radio signals with little to no interference. Trains run on the ground, often in valleys and tunnels. There is no guarantee that trains broadcasting "I am here" signals can be picked up by the next train within the stopping distance.
Many trains did broadcast "I am here" signals, but once speeds got faster, the broadcast range (about 1km) wasn't far enough for a train to stop in time before a collision, which is why trains need to communicate, using on-track wires that run the length of the track, to each other and central control. Which therefore means that the central control system needs to work, and when it doesn't, the trains have to stop.
Planes use radio signals because they don't have signalling cable following their entire route. Trains do, and it's usually much more reliable than radio.
Obviously it wouldn't be "just" GPS. In the simplest example - if I choose to add a friend to "Find my Friends" on iPhone, both our locations are visible to each other via GPS when our phones are on.
... via mobile data or WiFi, you mean. Whether it uses GPS, Galileo, track measurement points, or even "driver calls the control centre to update their position" doesn't have much to do with it. What I assume you mean is redundancy so that two or more systems can communicate train positions independently, where the more relevant problem is how to get the data across in a timely manner. The driver of the stationary train called in their position and it wasn't used: it's a communication problem, not a "where am I" problem. Idk why the focus on GPS and using GPS for communication (which GPS can't do, and newer systems only do at very low speeds for emergency communication) but finding one's position is usually not the problem
TCAS has solved this for airplanes. It wouldn't take much to modify the system for trains so that, in the least, it notifies when an unexpected train is nearby. A little more logic could allow it to verify which track each train is on.
This would fail at the first hurdle.
1. Planes can determine their altitude. Trains don't know which track they're on. You'd have to re-engineer existing signalling systems designed around the inverse. Track transponders and axle counters know which trainset passed a specific piece of track, but the trains don't know which track transponders link together on the same track. They don't even know which track they'll be going down next because that's up to the signallers controlling the points, not them.
2. Planes fly in the air and can send omnidirectional radio signals with little to no interference. Trains run on the ground, often in valleys and tunnels. There is no guarantee that trains broadcasting "I am here" signals can be picked up by the next train within the stopping distance.
Many trains did broadcast "I am here" signals, but once speeds got faster, the broadcast range (about 1km) wasn't far enough for a train to stop in time before a collision, which is why trains need to communicate, using on-track wires that run the length of the track, to each other and central control. Which therefore means that the central control system needs to work, and when it doesn't, the trains have to stop.
Planes use radio signals because they don't have signalling cable following their entire route. Trains do, and it's usually much more reliable than radio.
Obviously it wouldn't be "just" GPS. In the simplest example - if I choose to add a friend to "Find my Friends" on iPhone, both our locations are visible to each other via GPS when our phones are on.
> our locations are visible to each other via GPS
... via mobile data or WiFi, you mean. Whether it uses GPS, Galileo, track measurement points, or even "driver calls the control centre to update their position" doesn't have much to do with it. What I assume you mean is redundancy so that two or more systems can communicate train positions independently, where the more relevant problem is how to get the data across in a timely manner. The driver of the stationary train called in their position and it wasn't used: it's a communication problem, not a "where am I" problem. Idk why the focus on GPS and using GPS for communication (which GPS can't do, and newer systems only do at very low speeds for emergency communication) but finding one's position is usually not the problem
"Just put airtags on all the trains"... obviously simplistic but I get your point.