CBTC is more complicated than "a wifi network and servers" unfortunately. And it's not a great business. Firstly, no, WiFi is not going to work. WiFi runs in t

CBTC is more complicated than "a wifi network and servers" unfortunately. And it's not a great business. Firstly, no, WiFi is not going to work. WiFi runs in the junk bands like Bluetooth does. It's designed to run in unregulated spectrum, not be reliable, which is why WiFi is a synonym for "why does my internet not work today". Just think of interference from the riders phones, for example. You also need to know the location of the trains to a much higher degree of accuracy than what WiFi would allow. The trains use transponders on the track that antennae pass over. It's closer to NFC than WiFi. When the train knows where it is, it can communicate that info to the control rooms but trains spend a lot of time inside tunnels which are not exactly famous for their excellent radio propagation properties. There's a lot of testing and planning work required to figure out where to install antennas and cable uplinks. Remember that track maintenance hours are severely constrained on any live transit system so reducing the amount of equipment to install is important. Then you have redundancy. When your home wifi router goes on the fritz it's annoying but not that big a deal. If a part of the train monitoring network goes black, done naively that would shut down an entire line, which is catastrophic. So you want redundancy, you want spare parts inventories, you need to train staff how to do the replacements etc. Every train needs to be brought back to shop and refitted, usually using custom equipment and designs because trains are not standardised across the world. That's just the hardware. The software needs to be developed and tested too. Again, no standardisation in how transit systems work, so each deployment is a custom job requiring the engineers to have a good understanding of each railway with all its quirks and complexities, especially in exotic signalling and switching arrangements. Still, in the end, $19 billion is too much. The NY premium.