It is actually bonkers that in this day and age the NYC subway cannot install accurate speed gauges on their trains. You can get an accurate bike speedometer for $20 on amazon, but the NYC subway cannot provide an accurate speedometer for train carrying a couple of hundred people. It is true that trains require more rigorous standards, but it is not a difficult problem. For example you can put a sensor on the electrical motor that will accurately measure motor position. This will allow you to derive speed, as subway motors are directly geared to the wheels at a single unchanging gear ratio.
Same thing for stationary speed sensors in the signaling system. It is maddening that they have to time a train over a distance of 50 feet and use an electro-mechanical timing mechanism. Which has to be regularly maintained and it tends to give wrong readings when not properly maintained, etc. Why not get an instantaneous speed reading with lasers? Those have worked for police officers for 40 years now. Or infrared. Or if you have to time a train over a distance time it with a purely electronic system over a distance of a couple of inches. There are definitely electronics fast enough to do that nowadays. And you can get a purely electronic system that requires zero or almost zero maintenance.
Same thing for stationary speed sensors in the signaling system. It is maddening that they have to time a train over a distance of 50 feet and use an electro-mechanical timing mechanism. Which has to be regularly maintained and it tends to give wrong readings when not properly maintained, etc. Why not get an instantaneous speed reading with lasers? Those have worked for police officers for 40 years now. Or infrared. Or if you have to time a train over a distance time it with a purely electronic system over a distance of a couple of inches. There are definitely electronics fast enough to do that nowadays. And you can get a purely electronic system that requires zero or almost zero maintenance.