Some trains already to this, where they put in electronic valves in the air lines for in car. Basically, the electronic valve controls if the existing brake is

Some trains already to this, where they put in electronic valves in the air lines for in car. Basically, the electronic valve controls if the existing brake is vented or connected to the central air line. This still allows for the fail-safe behavior of being able to brake the train from the central air line by venting it. This lets them start easier/quicker from a stop, as they don't have to re-air the entire train and less wear on the brakes of the trains in the front of the train as all the cars start braking at the same time. This is particularly useful for trains that have to start on a hill as taking minutes for your brakes to fully turn off can complicate things.